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Wikipedia

XHTML

January 10, 2023

Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages. It mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated.

XHTML
Filename extension
.xhtml, .xht,
.xml, .html, .htm
Internet media type
application/xhtml+xml
Uniform Type Identifier (UTI)public.xhtml
UTI conformationpublic.xml
Developed byWorld Wide Web Consortium (W3C)
Initial release26 January 2000 (2000-01-26)
Latest release
5.0
28 October 2014; 8 years ago (2014-10-28)
Type of formatMarkup language
Extended fromXML, HTML
StandardW3C HTML5 (Recommendation)
Open format?Yes

While HTML, prior to HTML5, was defined as an application of Standard Generalized Markup Language (SGML), a flexible markup language framework, XHTML is an application of XML, a more restrictive subset of SGML. XHTML documents are well-formed and may therefore be parsed using standard XML parsers, unlike HTML, which requires a lenient HTML-specific parser.[1]

XHTML 1.0 became a World Wide Web Consortium (W3C) recommendation on 26 January 2000. XHTML 1.1 became a W3C recommendation on 31 May 2001. The standard known as XHTML5 is being developed as an XML adaptation of the HTML5 specification.[2][3]

Overview

XHTML 1.0 is "a reformulation of the three HTML 4 document types as applications of XML 1.0".[4] The World Wide Web Consortium (W3C) also continues to maintain the HTML 4.01 Recommendation, and the specifications for HTML5 and XHTML5 are being actively developed. In the current XHTML 1.0 Recommendation document, as published and revised in August 2002, the W3C commented that "The XHTML family is the next step in the evolution of the Internet. By migrating to XHTML today, content developers can enter the XML world with all of its attendant benefits, while still remaining confident in their content's backward and future compatibility."[4]

However, in 2005, the Web Hypertext Application Technology Working Group (WHATWG) formed, independently of the W3C, to work on advancing ordinary HTML not based on XHTML. The WHATWG eventually began working on a standard that supported both XML and non-XML serializations, HTML5, in parallel to W3C standards such as XHTML 2. In 2007, the W3C's HTML working group voted to officially recognize HTML5 and work on it as the next-generation HTML standard.[5] In 2009, the W3C allowed the XHTML 2 Working Group's charter to expire, acknowledging that HTML5 would be the sole next-generation HTML standard, including both XML and non-XML serializations.[6] Of the two serializations, the W3C suggests that most authors use the HTML syntax, rather than the XHTML syntax.[7]

Motivation

XHTML was developed to make HTML more extensible and increase interoperability with other data formats.[8] In addition, browsers were forgiving of errors in HTML, and most websites were displayed despite technical errors in the markup; XHTML introduced stricter error handling.[9] HTML 4 was ostensibly an application of Standard Generalized Markup Language (SGML); however the specification for SGML was complex, and neither web browsers nor the HTML 4 Recommendation were fully conformant to it.[10] The XML standard, approved in 1998, provided a simpler data format closer in simplicity to HTML 4.[11] By shifting to an XML format, it was hoped HTML would become compatible with common XML tools;[12] servers and proxies would be able to transform content, as necessary, for constrained devices such as mobile phones.[13] By using namespaces, XHTML documents could provide extensibility by including fragments from other XML-based languages such as Scalable Vector Graphics and MathML.[14] Finally, the renewed work would provide an opportunity to divide HTML into reusable components (XHTML Modularization) and clean up untidy parts of the language.[15]

Relationship to HTML

There are various differences between XHTML and HTML. The Document Object Model (DOM) is a tree structure that represents the page internally in applications, and XHTML and HTML are two different ways of representing that in markup. Both are less expressive than the DOM – for example, "--" may be placed in comments in the DOM, but cannot be represented in a comment in either XHTML or HTML – and generally, XHTML's XML syntax is more expressive than HTML (for example, arbitrary namespaces are not allowed in HTML). XHTML uses an XML syntax, while HTML uses a pseudo-SGML syntax (officially SGML for HTML 4 and under, but never in practice, and standardized away from SGML in HTML5). Because the expressible contents of the DOM in syntax are slightly different, there are some changes in actual behavior between the two models. Syntax differences, however, can be overcome by implementing an alternate translational framework within the markup.

First, there are some differences in syntax:[16]

  • Broadly, the XML rules require that all elements be closed, either by a separate closing tag or using the self-closing syntax (e.g. <br />), while HTML syntax permits some elements to be unclosed because either they are always empty (e.g. <input>) or their end can be determined implicitly ("omissibility", e.g. <p>).
  • XML is case-sensitive for element and attribute names, while HTML is not.
  • Some shorthand features in HTML are omitted in XML, such as (1) attribute minimization, where attribute values or their quotes may be omitted (e.g. <option selected> or <option selected=selected>, while in XML this must be expressed as <option selected="selected">); (2) element minimization may be used to remove elements entirely (such as <tbody> inferred in a table if not given); and (3) the rarely used SGML syntax for element minimization ("shorttag"), which most browsers do not implement.[17]
  • There are numerous other technical requirements surrounding namespaces and precise parsing of whitespace and certain characters and elements. The exact parsing of HTML in practice has been undefined until recently; see the HTML5 specification ([HTML5]) for full details, or the working summary (HTML vs. XHTML).

In addition to the syntactical differences, there are some behavioral differences, mostly arising from the underlying differences in serialization. For example:

  • Behavior on parse errors differs. A fatal parse error in XML (such as an incorrect tag structure) causes document processing to be aborted.
  • Most content requiring namespaces will not work in HTML, except the built-in support for SVG and MathML in the HTML5 parser along with certain magic prefixes such as xlink.
  • JavaScript processing is different in XHTML, with minor changes in case sensitivity to some functions, and further precautions to restrict processing to well-formed content. Scripts must not use the document.write() method; it is not available for XHTML. The innerHTML property is available, but will not insert non-well-formed content. On the other hand, it can be used to insert well-formed namespaced content into XHTML.
  • Cascading Style Sheets (CSS) are also applied differently. Due to XHTML's case-sensitivity, all CSS selectors become case-sensitive for XHTML documents.[18] Some CSS properties, such as backgrounds, set on the <body> element in HTML are 'inherited upwards' into the <html> element; this appears[clarification needed] not to be the case for XHTML.[19]

Adoption

The similarities between HTML 4.01 and XHTML 1.0 led many websites and content management systems to adopt the initial W3C XHTML 1.0 Recommendation. To aid authors in the transition, the W3C provided guidance on how to publish XHTML 1.0 documents in an HTML-compatible manner, and serve them to browsers that were not designed for XHTML.[20][21]

Such "HTML-compatible" content is sent using the HTML media type (text/html) rather than the official Internet media type for XHTML (application/xhtml+xml). When measuring the adoption of XHTML to that of regular HTML, therefore, it is important to distinguish whether it is media type usage or actual document contents that are being compared.[22][23]

Most web browsers have mature support[24] for all of the possible XHTML media types.[25] The notable exception is Internet Explorer versions 8 and earlier by Microsoft; rather than rendering application/xhtml+xml content, a dialog box invites the user to save the content to disk instead. Both Internet Explorer 7 (released in 2006) and Internet Explorer 8 (released in March 2009) exhibit this behavior.[26] Microsoft developer Chris Wilson explained in 2005 that IE7's priorities were improved browser security and CSS support, and that proper XHTML support would be difficult to graft onto IE's compatibility-oriented HTML parser;[27] however, Microsoft added support for true XHTML in IE9.[28]

As long as support is not widespread, most web developers avoid using XHTML that is not HTML-compatible,[29] so advantages of XML such as namespaces, faster parsing, and smaller-footprint browsers do not benefit the user.[30][31][32]

Criticism

In the early 2000s, some Web developers began to question why Web authors ever made the leap into authoring in XHTML.[33][34][35] Others countered that the problems ascribed to the use of XHTML could mostly be attributed to two main sources: the production of invalid XHTML documents by some Web authors and the lack of support for XHTML built into Internet Explorer 6.[36][37] They went on to describe the benefits of XML-based Web documents (i.e. XHTML) regarding searching, indexing, and parsing as well as future-proofing the Web itself.

In October 2006, HTML inventor and W3C chair Tim Berners-Lee, introducing a major W3C effort to develop a new HTML specification, posted in his blog that, "The attempt to get the world to switch to XML ... all at once didn't work. The large HTML-generating public did not move ... Some large communities did shift and are enjoying the fruits of well-formed systems ... The plan is to charter a completely new HTML group."[38] The current HTML5 working draft says "special attention has been given to defining clear conformance criteria for user agents in an effort to improve interoperability ... while at the same time updating the HTML specifications to address issues raised in the past few years." Ian Hickson, editor of the HTML5 specification criticizing the improper use of XHTML in 2002,[33] is a member of the group developing this specification and is listed as one of the co-editors of the current working draft.[39]

Simon Pieters researched the XML-compliance of mobile browsers[40] and concluded "the claim that XHTML would be needed for mobile devices is simply a myth".

Versions of XHTML

XHTML 1.0

 
In earlier times[when?], Wikipedia used the XHTML 1.0 Transitional doctype and syntax, though it was not served as XHTML

December 1998 saw the publication of a W3C Working Draft entitled Reformulating HTML in XML. This introduced Voyager, the codename for a new markup language based on HTML 4, but adhering to the stricter syntax rules of XML. By February 1999 the name of the specification had changed to XHTML 1.0: The Extensible HyperText Markup Language, and in January 2000 it was officially adopted as a W3C Recommendation.[41] There are three formal DTDs for XHTML 1.0, corresponding to the three different versions of HTML 4.01:

  • XHTML 1.0 Strict is the XML equivalent to strict HTML 4.01, and includes elements and attributes that have not been marked deprecated in the HTML 4.01 specification. As of November 2015, XHTML 1.0 Strict is the document type used for the homepage of the website of the World Wide Web Consortium.
  • XHTML 1.0 Transitional is the XML equivalent of HTML 4.01 Transitional, and includes the presentational elements (such as center, font and strike) excluded from the strict version.
  • XHTML 1.0 Frameset is the XML equivalent of HTML 4.01 Frameset, and allows for the definition of frameset documents—a common Web feature in the late 1990s.

The second edition of XHTML 1.0 became a W3C Recommendation in August 2002.[42]

Modularization of XHTML

Modularization provides an abstract collection of components through which XHTML can be subsetted and extended. The feature is intended to help XHTML extend its reach onto emerging platforms, such as mobile devices and Web-enabled televisions. The initial draft of Modularization of XHTML became available in April 1999, and reached Recommendation status in April 2001.[43]

The first modular XHTML variants were XHTML 1.1 and XHTML Basic 1.0.

In October 2008 Modularization of XHTML was superseded by XHTML Modularization 1.1, which adds an XML Schema implementation. It was superseded by a second edition in July 2010.[44]

XHTML 1.1: Module-based XHTML

XHTML 1.1 evolved out of the work surrounding the initial Modularization of XHTML specification. The W3C released the first draft in September 1999; the Recommendation status was reached in May 2001.[45] The modules combined within XHTML 1.1 effectively recreate XHTML 1.0 Strict, with the addition of ruby annotation elements (ruby, rbc, rtc, rb, rt and rp) to better support East-Asian languages. Other changes include the removal of the name attribute from the a and map elements, and (in the first edition of the language) the removal of the lang attribute in favor of xml: lang.

Although XHTML 1.1 is largely compatible with XHTML 1.0 and HTML 4, in August 2002 the Working Group issued a formal Note advising that it should not be transmitted with the HTML media type.[46] With limited browser support for the alternate application/xhtml+xml media type, XHTML 1.1 proved unable to gain widespread use. In January 2009 a second edition of the document (XHTML Media Types – Second Edition) was issued, relaxing this restriction and allowing XHTML 1.1 to be served as text/html.[47]

The second edition of XHTML 1.1 was issued on 23 November 2010, which addresses various errata and adds an XML Schema implementation not included in the original specification.[48] (It was first released briefly on 7 May 2009 as a "Proposed Edited Recommendation"[49] before being rescinded on 19 May due to unresolved issues.)

XHTML Basic

Main article: XHTML Basic

Since information appliances may lack the system resources to implement all XHTML abstract modules, the W3C defined a feature-limited XHTML specification called XHTML Basic. It provides a minimal feature subset sufficient for the most common content-authoring. The specification became a W3C recommendation in December 2000.[50]

Of all the versions of XHTML, XHTML Basic 1.0 provides the fewest features. With XHTML 1.1, it is one of the two first implementations of modular XHTML. In addition to the Core Modules (Structure, Text, Hypertext, and List), it implements the following abstract modules: Base, Basic Forms, Basic Tables, Image, Link, Metainformation, Object, Style Sheet, and Target.[51][52]

XHTML Basic 1.1 replaces the Basic Forms Module with the Forms Module and adds the Intrinsic Events, Presentation, and Scripting modules. It also supports additional tags and attributes from other modules. This version became a W3C recommendation on 29 July 2008.[53]

The current version of XHTML Basic is 1.1 Second Edition (23 November 2010), in which the language is re-implemented in the W3C's XML Schema language. This version also supports the lang attribute.[54]

XHTML-Print

XHTML-Print, which became a W3C Recommendation in September 2006, is a specialized version of XHTML Basic designed for documents printed from information appliances to low-end printers.[55]

XHTML Mobile Profile

Main article: XHTML Mobile Profile

XHTML Mobile Profile (abbreviated XHTML MP or XHTML-MP) is a third-party variant of the W3C's XHTML Basic specification. Like XHTML Basic, XHTML was developed for information appliances with limited system resources.

In October 2001, a limited company called the Wireless Application Protocol Forum began adapting XHTML Basic for WAP 2.0, the second major version of the Wireless Application Protocol. WAP Forum based their DTD on the W3C's Modularization of XHTML, incorporating the same modules the W3C used in XHTML Basic 1.0—except for the Target Module. Starting with this foundation, the WAP Forum replaced the Basic Forms Module with a partial implementation of the Forms Module, added partial support for the Legacy and Presentation modules, and added full support for the Style Attribute Module.

In 2002, the WAP Forum has subsumed into the Open Mobile Alliance (OMA), which continued to develop XHTML Mobile Profile as a component of their OMA Browsing Specification.

XHTML Mobile Profile 1.1

To this version, finalized in 2004, the OMA added partial support for the Scripting Module and partial support for Intrinsic Events. XHTML MP 1.1 is part of v2.1 of the OMA Browsing Specification (1 November 2002).[56]

XHTML Mobile Profile 1.2

This version, finalized on 27 February 2007, expands the capabilities of XHTML MP 1.1 with full support for the Forms Module and OMA Text Input Modes. XHTML MP 1.2 is part of v2.3 of the OMA Browsing Specification (13 March 2007).[56]

XHTML Mobile Profile 1.3

XHTML MP 1.3 (finalized on 23 September 2008) uses the XHTML Basic 1.1 document type definition, which includes the Target Module. Events in this version of the specification are updated to DOM Level 3 specifications (i.e., they are platform- and language-neutral).

XHTML 1.2

The XHTML 2 Working Group considered the creation of a new language based on XHTML 1.1.[57] If XHTML 1.2 was created, it would include WAI-ARIA and role attributes to better support accessible web applications, and improved Semantic Web support through RDFa. The inputmode attribute from XHTML Basic 1.1, along with the target attribute (for specifying frame targets) might also be present. The XHTML2 WG had not been chartered to carry out the development of XHTML1.2. Since the W3C announced that it does not intend to recharter the XHTML2 WG,[6] and closed the WG in December 2010, this means that XHTML 1.2 proposal would not eventuate.

XHTML 2.0

Between August 2002 and July 2006, the W3C released eight Working Drafts of XHTML 2.0, a new version of XHTML able to make a clean break from the past by discarding the requirement of backward compatibility. This lack of compatibility with XHTML 1.x and HTML 4 caused some early controversy in the web developer community.[58] Some parts of the language (such as the role and RDFa attributes) were subsequently split out of the specification and worked on as separate modules, partially to help make the transition from XHTML 1.x to XHTML 2.0 smoother. The ninth draft of XHTML 2.0 was expected to appear in 2009, but on 2 July 2009, the W3C decided to let the XHTML2 Working Group charter expire by that year's end, effectively halting any further development of the draft into a standard.[6] Instead, XHTML 2.0 and its related documents were released as W3C Notes in 2010.[59][60]

New features to have been introduced by XHTML 2.0 included:

  • HTML forms were to be replaced by XForms, an XML-based user input specification allowing forms to be displayed appropriately for different rendering devices.
  • HTML frames were to be replaced by XFrames.
  • The DOM Events were to be replaced by XML Events, which uses the XML Document Object Model.
  • A new list element type, the nl element type, was to be included to specifically designate a list as a navigation list. This would have been useful in creating nested menus, which are currently created by a wide variety of means like nested unordered lists or nested definition lists.
  • Any element was to be able to act as a hyperlink, e. g., <li href="articles.html">Articles</li>, similar to XLink. However, XLink itself is not compatible with XHTML due to design differences.
  • Any element was to be able to reference alternative media with the src attribute, e. g., <p src="lbridge.jpg" type="image/jpeg">London Bridge</p> is the same as <object src="lbridge.jpg" type="image/jpeg"><p>London Bridge</p></object>.
  • The alt attribute of the img element was removed: alternative text was to be given in the content of the img element, much like the object element, e. g., <img src="hms_audacious.jpg">HMS <span class="italic">Audacious</span></img>.
  • A single heading element (h) was added. The level of these headings was determined by the depth of the nesting. This would have allowed the use of headings to be infinite, rather than limiting use to six levels deep.
  • The remaining presentational elements i, b and tt, still allowed in XHTML 1.x (even Strict), were to be absent from XHTML 2.0. The only somewhat presentational elements remaining were to be sup and sub for superscript and subscript respectively because they have significant non-presentational uses and are required by certain languages. All other tags were meant to be semantic instead (e. g. strong for strong emphasis) while allowing the user agent to control the presentation of elements via CSS (e.g. rendered as boldface text in most visual browsers, but possibly rendered with changes of tone in a text-to-speech reader, larger + italic font per rules in a user-end stylesheet, etc.).
  • The addition of RDF triple with the property and about attributes to facilitate the conversion from XHTML to RDF/XML.

XHTML5

Main article: XHTML5

HTML5 grew independently of the W3C, through a loose group of browser manufacturers and other interested parties calling themselves the WHATWG, or Web Hypertext Application Technology Working Group. The key motive of the group was to create a platform for dynamic web applications; they considered XHTML 2.0 to be too document-centric, and not suitable for the creation of internet forum sites or online shops.[61]

HTML5 has both a regular text/html serialization and an XML serialization, which is also known as XHTML5.[62] The language is more compatible with HTML 4 and XHTML 1.x than XHTML 2.0, due to the decision to keep the existing HTML form elements and events model. It adds many new elements not found in XHTML 1. x, however, such as section and aside tags.

The XHTML5 language, like HTML5, uses a DOCTYPE declaration without a DTD. Furthermore, the specification deprecates earlier XHTML DTDs by asking the browsers to replace them with one containing only entity definitions for named characters during parsing.[62]

Semantic content in XHTML

XHTML+RDFa is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. This host language is one of the techniques used to develop Semantic Web content by embedding rich semantic markup.

Valid XHTML documents

An XHTML document that conforms to an XHTML specification is said to be valid. Validity assures consistency in document code, which in turn eases processing, but does not necessarily ensure consistent rendering by browsers. A document can be checked for validity with the W3C Markup Validation Service (for XHTML5, the Validator. nu Living Validator should be used instead). In practice, many web development programs provide code validation based on the W3C standards.

Root element

The root element of an XHTML document must be html, and must contain an xmlns attribute to associate it with the XHTML namespace. The namespace URI for XHTML is http://www.w3.org/1999/xhtml. The example tag below additionally features an xml:lang attribute to identify the document with a natural language: 

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="ar">

DOCTYPEs

Main article: DOCTYPE

In order to validate an XHTML document, a Document Type Declaration, or DOCTYPE, may be used. A DOCTYPE declares to the browser the Document Type Definition (DTD) to which the document conforms. A Document Type Declaration should be placed before the root element.

The system identifier part of the DOCTYPE, which in these examples is the URL that begins with http://, need only point to a copy of the DTD to use, if the validator cannot locate one based on the public identifier (the other quoted string). It does not need to be the specific URL that is in these examples; in fact, authors are encouraged to use local copies of the DTD files when possible. The public identifier, however, must be character-for-character the same as in the examples.

XML declaration

See also: Processing Instruction

A character encoding may be specified at the beginning of an XHTML document in the XML declaration when the document is served using the application/xhtml+xml MIME type. (If an XML document lacks encoding specification, an XML parser assumes that the encoding is UTF-8 or UTF-16, unless the encoding has already been determined by a higher protocol.)

For example:

<?xml version="1.0" encoding="UTF-8" ?>

The declaration may be optionally omitted because it declares its encoding the default encoding. However, if the document instead makes use of XML 1.1 or another character encoding, a declaration is necessary. Internet Explorer prior to version 7 enters quirks mode, if it encounters an XML declaration in a document served as text/html.

Backward compatibility

XHTML 1.x documents are mostly backward compatible with HTML 4 user agents when the appropriate guidelines are followed. XHTML 1.1 is essentially compatible, although the elements for ruby annotation are not part of the HTML 4 specification and thus generally ignored by HTML 4 browsers. Later XHTML 1.x modules such as those for the role attribute, RDFa, and WAI-ARIA degrade gracefully in a similar manner.

XHTML 2.0 is significantly less compatible, although this can be mitigated to some degree through the use of scripting. (This can be simple one-liners, such as the use of document.createElement() to register a new HTML element within Internet Explorer, or complete JavaScript frameworks, such as the FormFaces implementation of XForms.)

Examples

The following are examples of XHTML 1.0 Strict, with both having the same visual output. The former one follows the HTML Compatibility Guidelines of the XHTML Media Types Note while the latter one breaks backward compatibility, but provides cleaner markup.[47]

Media type recommendation (in RFC 2119 terms) for the examples:
Media type Example 1 Example 2
application/xhtml+xml SHOULD SHOULD
application/xml MAY MAY
text/xml MAY MAY
text/html MAY SHOULD NOT

Example 1. 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>XHTML 1.0 Strict Example</title> <script type="text/javascript"> //<![CDATA[  function loadpdf() {  document.getElementById("pdf-object").src="http://www.w3.org/TR/xhtml1/xhtml1.pdf";  }  //]]> </script> </head> <body onload="loadpdf()"> <p>This is an example of an <abbr title="Extensible HyperText Markup Language">XHTML</abbr> 1.0 Strict document.<br /> <img id="validation-icon" src="http://www.w3.org/Icons/valid-xhtml10" alt="Valid XHTML 1.0 Strict"/><br /> <object id="pdf-object" name="pdf-object" type="application/pdf" data="http://www.w3.org/TR/xhtml1/xhtml1.pdf" width="100%" height="500"> </object> </p> </body> </html>

Example 2. 

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <title>XHTML 1.0 Strict Example</title> <script type="application/javascript"> <![CDATA[  function loadpdf() {  document.getElementById("pdf-object").src="http://www.w3.org/TR/xhtml1/xhtml1.pdf";  }  ]]> </script> </head> <body onload="loadpdf()"> <p>This is an example of an <abbr title="Extensible HyperText Markup Language">XHTML</abbr> 1.0 Strict document.<br /> <img id="validation-icon" src="http://www.w3.org/Icons/valid-xhtml10" alt="Valid XHTML 1.0 Strict"/><br /> <object id="pdf-object" type="application/pdf" data="http://www.w3.org/TR/xhtml1/xhtml1.pdf" width="100%" height="500"></object> </p> </body> </html>

Notes:

  1. The "loadpdf" function is actually a workaround for Internet Explorer. It can be replaced by adding <param name="src" value="http://www.w3.org/TR/xhtml1/xhtml1.pdf"/> within <object>.
  2. The img element does not get a name attribute in the XHTML 1.0 Strict DTD. Use id instead.

Cross-compatibility of XHTML and HTML

HTML5 and XHTML5 serializations are largely inter-compatible if adhering to the stricter XHTML5 syntax, but there are some cases in which XHTML will not work as valid HTML5 (e.g., processing instructions are deprecated in HTML[clarify], are treated as comments, and close on the first ">", whereas they are fully allowed in XML, are treated as their own type, and close on ?>).[63]

See also

References

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  3. ^ "The WHATWG Blog". whatwg.org.
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  5. ^ "results of HTML 5 text, editor, name questions". w3.org.
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  10. ^ Arjun Ray (1999-10-06). "Dropping the Normative Reference to SGML (was: I-D ACTION.)". Retrieved 2008-12-29. ... However, since ISO 8879 does not afford applications the leeway to prohibit internal subsets, it follows that the letter of the HTML [4] spec automatically disentitles it to be a conforming SGML application...
  11. ^ Tina Holmboe (2008-10-06). . The Developer's Archive. Archived from the original on 2017-01-12. Retrieved 2008-12-29. ... Since the design goals of XML itself partially mirrored those of the original HTML, it was logical for work to begin on formulating an XML–based markup language...
  12. ^ Kip Hampton (2001-01-10). "Creating Web Utilities Using XML::XPath". XML.com. Retrieved 2008-12-29. ... The problem: You want to take advantage of the power and simplicity that XML tools can offer, but you face a site full of aging HTML documents. The solution: Convert your documents to XHTML and put Perl and XML::XPath to work...
  13. ^ Jean-Luc David (2004-04-14). "Developing Wireless Content using XHTML Mobile". XML.com. Retrieved 2008-12-29. ... A useful feature of XHTML is that it can be manipulated as XML. Extensible Stylesheet Language Templates can be used to transform XHTML into WML or any other proprietary mobile formats...
  14. ^ . Mozilla Developer Center. Archived from the original on 2008-10-02. Retrieved 2008-12-29. ... It has been a long-standing goal of the W3C to make it possible for different types of XML-based content to be mixed together in the same XML file. For example, SVG and MathML might be incorporated directly into an XHTML-based scientific document...
  15. ^ Steven Pemberton (2004-07-21). "HTML and XHTML Frequently Answered Questions". World Wide Web Consortium. Retrieved 2008-12-29. ... with an XML-based HTML other XML languages could include bits of XHTML, and XHTML documents could include bits of other markup languages. We could also take advantage of the redesign to clean up some of the more untidy parts of HTML and add some new needed functionality, like better forms...
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  18. ^ "Case Sensitivity". SitePoint Pty. Ltd. Retrieved 30 September 2011.
  19. ^ Wilson, Nicholas. "CSS differences between XHTML and HTML".
  20. ^ "XHTML 1.0 Specification, Appendix C: HTML Compatibility Guidelines". World Wide Web Consortium. 2000-01-26. Retrieved 2007-06-16.
  21. ^ "XHTML Media Types, W3C Working Group Note". World Wide Web Consortium. 2002-08-01. Retrieved 2008-06-12.
  22. ^ "Meta and Inline Tags that Google Understands | Google Search Central".
  23. ^ Greta de Groat (2002). "Perspectives on the Web and Google: Monika Henzinger, Director of Research, Google", Journal of Internet Cataloging, Vol. 5(1), pp. 17-28, 2002.
  24. ^ Early implementations (such as Mozilla 0.7 and Opera 6.0, both released in 2001) do not incrementally render XHTML as it is received over the network, giving a degraded user experience; see the Mozilla Web Author FAQ. Later browsers such as Opera 9.0, Safari 3.0, and Firefox 3.0 do not have this issue.
  25. ^ "XHTML media type test - results". w3.org.
  26. ^ Chris Wilson (2005-09-15). "The <?xml> prolog, strict mode, and XHTML in IE". Retrieved 2007-06-16. I've also been reading comments for some time in the IEBlog asking for support for the "application/xml+xhtml" MIME type in IE. I should say that IE7 will not add support for this MIME type – we will, of course, continue to read XHTML when served as "text/html", presuming it follows the HTML compatibility recommendations.
  27. ^ Chris Wilson (2005-09-15). "The <?xml> prolog, strict mode, and XHTML in IE". Retrieved 2007-06-16. ...If we tried to support real XHTML in IE 7 we would have ended up using our existing HTML parser (which is focused on compatibility) and hacking in XML constructs. It is highly unlikely we could support XHTML well in this way; in particular, we would certainly not detect a few error cases here or there, and we would silently support invalid cases. This would, of course, cause compatibility problems based on parser error handling in the future, which XML is explicitly trying to avoid; we don't want to cause another mess like the one with current HTML error handling (rooted in compatibility with earlier browsers – you can blame me for that personally somewhat, but not IE). I would much rather take the time to implement XHTML properly after IE 7, and have it be truly interoperable...
  28. ^ Hachamovitch, Dean (2010-03-16). "HTML5, Hardware Accelerated: First IE9 Platform Preview Available for Developers". IEBlog on Microsoft Developer Network. Microsoft. Retrieved 2010-03-22. ...At this time, we're looking for developer feedback on our implementation of HTML5's parsing rules, Selection APIs, XHTML support, and inline SVG. Within CSS3, we're looking for developer feedback on IE9's support for Selectors, Namespaces, Colors, Values, Backgrounds and Borders, and Fonts....
  29. ^ "List of XHTML Sites (the X-Philes)". Retrieved 2008-08-26.
  30. ^ "In 2007, 37 leaders in search engine optimisation concluded that having keywords in the keywords attribute is little to none." Sanger. nu blog, September 9, 2008, Retrieved August 2 2011 February 21, 2009, at the Wayback Machine
  31. ^ "Meta used for SEO". 18 December 2015. from the original on March 31, 2016. Retrieved March 18, 2016.
  32. ^ Danny Sullivan, How To Use HTML Meta Tags 2008-09-13 at the Wayback Machine, Search Engine Watch, December 5, 2002
  33. ^ a b Ian Hickson, a former developer of the Opera browser and cofounder of the WHATWG (2002-09-08). "Sending XHTML as text/html Considered Harmful". Retrieved 2007-06-16.
  34. ^ Anne van Kesteren, a developer of the Opera browser (2004-06-13). "XHTML is invalid HTML". Retrieved 2007-06-16.
  35. ^ Maciej Stachowiak, a developer of Apple's Safari browser (2006-09-20). "Understanding HTML, XML, and XHTML". Retrieved 2007-06-16.
  36. ^ Brad Fults (2005-12-21). "Sending XHTML as text/HTML Considered Harmful to Feelings". Retrieved 2008-09-13. There are not nearly as many disadvantages (if any) to sending XHTML as text/HTML as [Ian Hickson] claims and the advantages I mentioned above make it well worth using in my humble opinion. There are some subtle footnotes and parentheticals [in Hickson's article] indicating that the harmfulness only applies to authors that don't know the pitfalls of this practice, but much like the "Do not eat" label on the little packets of silica gel, Ian's advisory seems to be common sense and not worth mentioning to any author who actually knows what XHTML is and how to write it.
  37. ^ Paul McDonald (2007-06-30). "The case for XHTML". Retrieved 2008-09-13. Some people say XHTML on the Web has failed, but I say it is our biggest success in the fight for Web Standards. ... XHTML is a good thing for the web, though, and it's a shame that people are trying to make a case against it. To prove this, I'll flesh out the myth for you and then show you why XHTML is the best thing since sliced bread when it comes to our fight for Web Standards. ... So to conclude, sending XHTML as text/html causes no damage or harm anywhere today, as long as your XHTML does validate. And, if you want Web Standards to become more and more widespread, stick to using XHTML and validate your pages.
  38. ^ Tim Berners-Lee (2006-10-27). . Archived from the original on 2007-06-09. Retrieved 2007-06-16. Some things are clearer with the hindsight of several years. It is necessary to evolve HTML incrementally. The attempt to get the world to switch to XML, including quotes around attribute values and slashes in empty tags and namespaces all at once didn't work. The large HTML-generating public did not move, largely because the browsers didn't complain. Some large communities did shift and are enjoying the fruits of well-formed systems, but not all. It is important to maintain HTML incrementally, as well as continue a transition to [a] well-formed world, and develop more power in that world.
    "The plan is to charter a completely new HTML group. Unlike the previous one, this one will be chartered to do incremental improvements to HTML, as also in parallel XHTML. It will have a different chair and staff contact. It will work on HTML and xHTML together. We have strong support for this group, from many people we have talked to, including browser makers.
  39. ^ Ian Hickson; David Hyatt (2011-01-13). "HTML5: A vocabulary and associated APIs for HTML and XHTML". Retrieved 2011-02-16.
  40. ^ Simon Pieters. "Results of mobile tests". Retrieved 2009-10-31.
  41. ^ "XHTML 1.0: The Extensible HyperText Markup Language, W3C Recommendation 26 January 2000". World Wide Web Consortium. 2000-01-26. Retrieved 2008-07-19.
  42. ^ "XHTML 1.0 The Extensible HyperText Markup Language (Second Edition)". World Wide Web Consortium. 2002-08-01. Retrieved 2008-07-19.
  43. ^ "Modularization of XHTML, W3C Recommendation 10 April 2001". World Wide Web Consortium. 2001-04-10. Retrieved 2008-07-19.
  44. ^ "XHTML Modularization 1.1 - Second Edition, W3C Recommendation 29 July 2010". World Wide Web Consortium. 2010-07-29. Retrieved 2010-12-31.
  45. ^ "XHTML 1.1 - Module-based XHTML, W3C Recommendation 31 May 2001". World Wide Web Consortium. 2001-05-31. Retrieved 2008-07-19.
  46. ^ "XHTML Media Types, W3C Working Group Note 1 August 2002". World Wide Web Consortium. 2002-08-01. Retrieved 2008-07-19.
  47. ^ a b "XHTML Media Types – Second Edition, W3C Working Group Note 16 January 2009". World Wide Web Consortium. 2009-01-16. Retrieved 2009-01-28. This document supersedes the HTML Compatibility Guidelines originally found in XHTML 1.0 Appendix C.
  48. ^ "XHTML 1.1, XHTML Basic 1.1, XHTML Print Recommendations Revised". W3C NEWS ARCHIVE: 2010. World Wide Web Consortium. Retrieved 12 December 2010.
  49. ^ . World Wide Web Consortium. 2009-05-07. Archived from the original on 2009-05-12. Retrieved 2009-05-25.
  50. ^ "XHTML Basic, W3C Recommendation 19 December 2000". World Wide Web Consortium. 2000-12-19. Retrieved 2008-07-19.
  51. ^ "XHTML Flavors comparisons". World Wide Web Consortium. 2007-01-09. Retrieved 2013-01-30.
  52. ^ XHTML Basic. W3.org. Retrieved on 2013-07-17.
  53. ^ XHTML Basic 1.1. W3.org. Retrieved on 2013-07-17.
  54. ^ "XHTML Basic 1.1 - Second Edition". w3.org.
  55. ^ "XHTML-Print, W3C Recommendation 20 September 2006". World Wide Web Consortium. 2006-09-20. Retrieved 2008-07-19.
  56. ^ a b "OMA Browsing Archive". OMA Releases. Open Mobile Alliance Ltd. 26 September 2011.
  57. ^ "[XHTML] Agenda: 2008-07-09". w3.org.
  58. ^ See both XHTML 2.0 Considered Harmful and XHTML 2.0 Considered Hopeful by browser developer Tantek Çelik, who criticizes early drafts of XHTML 2.0 for the absence of the style attribute and the cite element. Developer Daniel Glazman offers similar criticism, but also shows support for some backward-incompatible changes such as the decision to remove the ins and del elements.
  59. ^ "XHTML 2.0, W3C Working Group Note 16 December 2010". World Wide Web Consortium. 2010-12-16. Retrieved 2010-12-31.
  60. ^ "XHTML2 Working Group Documents Published as W3C Notes". World Wide Web Consortium. 2010-12-16. Retrieved 2010-12-31.
  61. ^ Ian Hickson (2008-01-22). "HTML 5, 1.1.2. Relationship to XHTML2". World Wide Web Consortium. Retrieved 2008-07-19. ... XHTML2... defines a new HTML vocabulary with better features for hyperlinks, multimedia content, annotating document edits, rich metadata, declarative interactive forms, and describing the semantics of human literary works such as poems and scientific papers... However, it lacks elements to express the semantics of many of the non-document types of content often seen on the Web. For instance, forum sites, auction sites, search engines, online shops, and the like, do not fit the document metaphor well and are not covered by XHTML2... This specification aims to extend HTML so that it is also suitable in these contexts...
  62. ^ a b "9 The XHTML syntax — HTML5". w3.org.
  63. ^ HTML vs. XHTML, WHATWG Wiki

External links

 
Wikibooks has a book on the topic of: XHTML
  • W3C's Markup Home Page
  • XHTML 1.0 Recommendation
  • XHTML 1.1 Recommendation
  • XHTML 2.0 Working Group Note
  • XHTML Basic
  • XHTML 1.0 Strict / 1.1 Online Reference
  • Links dealing with the MIME type of XHTML documents:
    • Beware of XHTML
    • Sending XHTML as text/html Considered Harmful
    • Serving up XHTML with the correct MIME type
    • The Road to XHTML 2.0: MIME Types – Mark Pilgrim (3/19/2003). Includes examples for conditionally serving application/xhtml+xml using PHP, Python, and Apache (via URL rewriting).
    • Mozilla Web Author FAQ: How is the treatment of application/xhtml+xml documents different from the treatment of text/html documents? – summarizes one web browser's XHTML processing mode
  • Empty elements in SGML, HTML, XML, and XHTML
  • Heptagrama's Basic XHTML 1.0 Strict Tutorial
  • W3C's Markup Validator
  • HTML to XHTML conversion library for .NET

January 10, 2023
xhtml, extensible, hypertext, markup, language, part, family, markup, languages, mirrors, extends, versions, widely, used, hypertext, markup, language, html, language, which, pages, formulated, filename, extension, xhtml, html, htminternet, media, typeapplicat. Extensible HyperText Markup Language XHTML is part of the family of XML markup languages It mirrors or extends versions of the widely used HyperText Markup Language HTML the language in which Web pages are formulated XHTMLFilename extension xhtml xht xml html htmInternet media typeapplication xhtml xmlUniform Type Identifier UTI public xhtmlUTI conformationpublic xmlDeveloped byWorld Wide Web Consortium W3C Initial release26 January 2000 2000 01 26 Latest release5 028 October 2014 8 years ago 2014 10 28 Type of formatMarkup languageExtended fromXML HTMLStandardW3C HTML5 Recommendation Open format YesWhile HTML prior to HTML5 was defined as an application of Standard Generalized Markup Language SGML a flexible markup language framework XHTML is an application of XML a more restrictive subset of SGML XHTML documents are well formed and may therefore be parsed using standard XML parsers unlike HTML which requires a lenient HTML specific parser 1 XHTML 1 0 became a World Wide Web Consortium W3C recommendation on 26 January 2000 XHTML 1 1 became a W3C recommendation on 31 May 2001 The standard known as XHTML5 is being developed as an XML adaptation of the HTML5 specification 2 3 Contents 1 Overview 1 1 Motivation 1 2 Relationship to HTML 1 3 Adoption 1 4 Criticism 2 Versions of XHTML 2 1 XHTML 1 0 2 2 Modularization of XHTML 2 3 XHTML 1 1 Module based XHTML 2 4 XHTML Basic 2 4 1 XHTML Print 2 5 XHTML Mobile Profile 2 5 1 XHTML Mobile Profile 1 1 2 5 2 XHTML Mobile Profile 1 2 2 5 3 XHTML Mobile Profile 1 3 2 6 XHTML 1 2 2 7 XHTML 2 0 2 8 XHTML5 3 Semantic content in XHTML 4 Valid XHTML documents 4 1 Root element 4 2 DOCTYPEs 4 3 XML declaration 5 Backward compatibility 5 1 Examples 6 Cross compatibility of XHTML and HTML 7 See also 8 References 9 External linksOverview EditXHTML 1 0 is a reformulation of the three HTML 4 document types as applications of XML 1 0 4 The World Wide Web Consortium W3C also continues to maintain the HTML 4 01 Recommendation and the specifications for HTML5 and XHTML5 are being actively developed In the current XHTML 1 0 Recommendation document as published and revised in August 2002 the W3C commented that The XHTML family is the next step in the evolution of the Internet By migrating to XHTML today content developers can enter the XML world with all of its attendant benefits while still remaining confident in their content s backward and future compatibility 4 However in 2005 the Web Hypertext Application Technology Working Group WHATWG formed independently of the W3C to work on advancing ordinary HTML not based on XHTML The WHATWG eventually began working on a standard that supported both XML and non XML serializations HTML5 in parallel to W3C standards such as XHTML 2 In 2007 the W3C s HTML working group voted to officially recognize HTML5 and work on it as the next generation HTML standard 5 In 2009 the W3C allowed the XHTML 2 Working Group s charter to expire acknowledging that HTML5 would be the sole next generation HTML standard including both XML and non XML serializations 6 Of the two serializations the W3C suggests that most authors use the HTML syntax rather than the XHTML syntax 7 Motivation Edit XHTML was developed to make HTML more extensible and increase interoperability with other data formats 8 In addition browsers were forgiving of errors in HTML and most websites were displayed despite technical errors in the markup XHTML introduced stricter error handling 9 HTML 4 was ostensibly an application of Standard Generalized Markup Language SGML however the specification for SGML was complex and neither web browsers nor the HTML 4 Recommendation were fully conformant to it 10 The XML standard approved in 1998 provided a simpler data format closer in simplicity to HTML 4 11 By shifting to an XML format it was hoped HTML would become compatible with common XML tools 12 servers and proxies would be able to transform content as necessary for constrained devices such as mobile phones 13 By using namespaces XHTML documents could provide extensibility by including fragments from other XML based languages such as Scalable Vector Graphics and MathML 14 Finally the renewed work would provide an opportunity to divide HTML into reusable components XHTML Modularization and clean up untidy parts of the language 15 Relationship to HTML Edit There are various differences between XHTML and HTML The Document Object Model DOM is a tree structure that represents the page internally in applications and XHTML and HTML are two different ways of representing that in markup Both are less expressive than the DOM for example may be placed in comments in the DOM but cannot be represented in a comment in either XHTML or HTML and generally XHTML s XML syntax is more expressive than HTML for example arbitrary namespaces are not allowed in HTML XHTML uses an XML syntax while HTML uses a pseudo SGML syntax officially SGML for HTML 4 and under but never in practice and standardized away from SGML in HTML5 Because the expressible contents of the DOM in syntax are slightly different there are some changes in actual behavior between the two models Syntax differences however can be overcome by implementing an alternate translational framework within the markup First there are some differences in syntax 16 Broadly the XML rules require that all elements be closed either by a separate closing tag or using the self closing syntax e g span class nt lt br span span class nt gt span while HTML syntax permits some elements to be unclosed because either they are always empty e g span class p lt span span class nt input span span class p gt span or their end can be determined implicitly omissibility e g span class p lt span span class nt p span span class p gt span XML is case sensitive for element and attribute names while HTML is not Some shorthand features in HTML are omitted in XML such as 1 attribute minimization where attribute values or their quotes may be omitted e g span class p lt span span class nt option span span class na selected span span class p gt span or span class p lt span span class nt option span span class na selected span span class o span span class s selected span span class p gt span while in XML this must be expressed as span class nt lt option span span class na selected span span class s selected span span class nt gt span 2 element minimization may be used to remove elements entirely such as span class nt lt tbody gt span inferred in a table if not given and 3 the rarely used SGML syntax for element minimization shorttag which most browsers do not implement 17 There are numerous other technical requirements surrounding namespaces and precise parsing of whitespace and certain characters and elements The exact parsing of HTML in practice has been undefined until recently see the HTML5 specification HTML5 for full details or the working summary HTML vs XHTML In addition to the syntactical differences there are some behavioral differences mostly arising from the underlying differences in serialization For example Behavior on parse errors differs A fatal parse error in XML such as an incorrect tag structure causes document processing to be aborted Most content requiring namespaces will not work in HTML except the built in support for SVG and MathML in the HTML5 parser along with certain magic prefixes such as xlink JavaScript processing is different in XHTML with minor changes in case sensitivity to some functions and further precautions to restrict processing to well formed content Scripts must not use the span class nb document span span class p span span class nx write span span class p span method it is not available for XHTML The innerHTML property is available but will not insert non well formed content On the other hand it can be used to insert well formed namespaced content into XHTML Cascading Style Sheets CSS are also applied differently Due to XHTML s case sensitivity all CSS selectors become case sensitive for XHTML documents 18 Some CSS properties such as backgrounds set on the span class p lt span span class nt body span span class p gt span element in HTML are inherited upwards into the span class p lt span span class nt html span span class p gt span element this appears clarification needed not to be the case for XHTML 19 Adoption Edit The similarities between HTML 4 01 and XHTML 1 0 led many websites and content management systems to adopt the initial W3C XHTML 1 0 Recommendation To aid authors in the transition the W3C provided guidance on how to publish XHTML 1 0 documents in an HTML compatible manner and serve them to browsers that were not designed for XHTML 20 21 Such HTML compatible content is sent using the HTML media type text html rather than the official Internet media type for XHTML application xhtml xml When measuring the adoption of XHTML to that of regular HTML therefore it is important to distinguish whether it is media type usage or actual document contents that are being compared 22 23 Most web browsers have mature support 24 for all of the possible XHTML media types 25 The notable exception is Internet Explorer versions 8 and earlier by Microsoft rather than rendering application xhtml xml content a dialog box invites the user to save the content to disk instead Both Internet Explorer 7 released in 2006 and Internet Explorer 8 released in March 2009 exhibit this behavior 26 Microsoft developer Chris Wilson explained in 2005 that IE7 s priorities were improved browser security and CSS support and that proper XHTML support would be difficult to graft onto IE s compatibility oriented HTML parser 27 however Microsoft added support for true XHTML in IE9 28 As long as support is not widespread most web developers avoid using XHTML that is not HTML compatible 29 so advantages of XML such as namespaces faster parsing and smaller footprint browsers do not benefit the user 30 31 32 Criticism Edit In the early 2000s some Web developers began to question why Web authors ever made the leap into authoring in XHTML 33 34 35 Others countered that the problems ascribed to the use of XHTML could mostly be attributed to two main sources the production of invalid XHTML documents by some Web authors and the lack of support for XHTML built into Internet Explorer 6 36 37 They went on to describe the benefits of XML based Web documents i e XHTML regarding searching indexing and parsing as well as future proofing the Web itself In October 2006 HTML inventor and W3C chair Tim Berners Lee introducing a major W3C effort to develop a new HTML specification posted in his blog that The attempt to get the world to switch to XML all at once didn t work The large HTML generating public did not move Some large communities did shift and are enjoying the fruits of well formed systems The plan is to charter a completely new HTML group 38 The current HTML5 working draft says special attention has been given to defining clear conformance criteria for user agents in an effort to improve interoperability while at the same time updating the HTML specifications to address issues raised in the past few years Ian Hickson editor of the HTML5 specification criticizing the improper use of XHTML in 2002 33 is a member of the group developing this specification and is listed as one of the co editors of the current working draft 39 Simon Pieters researched the XML compliance of mobile browsers 40 and concluded the claim that XHTML would be needed for mobile devices is simply a myth Versions of XHTML EditXHTML 1 0 Edit In earlier times when Wikipedia used the XHTML 1 0 Transitional doctype and syntax though it was not served as XHTML December 1998 saw the publication of a W3C Working Draft entitled Reformulating HTML in XML This introduced Voyager the codename for a new markup language based on HTML 4 but adhering to the stricter syntax rules of XML By February 1999 the name of the specification had changed to XHTML 1 0 The Extensible HyperText Markup Language and in January 2000 it was officially adopted as a W3C Recommendation 41 There are three formal DTDs for XHTML 1 0 corresponding to the three different versions of HTML 4 01 XHTML 1 0 Strict is the XML equivalent to strict HTML 4 01 and includes elements and attributes that have not been marked deprecated in the HTML 4 01 specification As of November 2015 update XHTML 1 0 Strict is the document type used for the homepage of the website of the World Wide Web Consortium XHTML 1 0 Transitional is the XML equivalent of HTML 4 01 Transitional and includes the presentational elements such as center font and strike excluded from the strict version XHTML 1 0 Frameset is the XML equivalent of HTML 4 01 Frameset and allows for the definition of frameset documents a common Web feature in the late 1990s The second edition of XHTML 1 0 became a W3C Recommendation in August 2002 42 Modularization of XHTML Edit Modularization provides an abstract collection of components through which XHTML can be subsetted and extended The feature is intended to help XHTML extend its reach onto emerging platforms such as mobile devices and Web enabled televisions The initial draft of Modularization of XHTML became available in April 1999 and reached Recommendation status in April 2001 43 The first modular XHTML variants were XHTML 1 1 and XHTML Basic 1 0 In October 2008 Modularization of XHTML was superseded by XHTML Modularization 1 1 which adds an XML Schema implementation It was superseded by a second edition in July 2010 44 XHTML 1 1 Module based XHTML Edit XHTML 1 1 evolved out of the work surrounding the initial Modularization of XHTML specification The W3C released the first draft in September 1999 the Recommendation status was reached in May 2001 45 The modules combined within XHTML 1 1 effectively recreate XHTML 1 0 Strict with the addition of ruby annotation elements ruby rbc rtc rb rt and rp to better support East Asian languages Other changes include the removal of the name attribute from the a and map elements and in the first edition of the language the removal of the lang attribute in favor of xml lang Although XHTML 1 1 is largely compatible with XHTML 1 0 and HTML 4 in August 2002 the Working Group issued a formal Note advising that it should not be transmitted with the HTML media type 46 With limited browser support for the alternate application xhtml xml media type XHTML 1 1 proved unable to gain widespread use In January 2009 a second edition of the document XHTML Media Types Second Edition was issued relaxing this restriction and allowing XHTML 1 1 to be served as text html 47 The second edition of XHTML 1 1 was issued on 23 November 2010 which addresses various errata and adds an XML Schema implementation not included in the original specification 48 It was first released briefly on 7 May 2009 as a Proposed Edited Recommendation 49 before being rescinded on 19 May due to unresolved issues XHTML Basic Edit Main article XHTML Basic Since information appliances may lack the system resources to implement all XHTML abstract modules the W3C defined a feature limited XHTML specification called XHTML Basic It provides a minimal feature subset sufficient for the most common content authoring The specification became a W3C recommendation in December 2000 50 Of all the versions of XHTML XHTML Basic 1 0 provides the fewest features With XHTML 1 1 it is one of the two first implementations of modular XHTML In addition to the Core Modules Structure Text Hypertext and List it implements the following abstract modules Base Basic Forms Basic Tables Image Link Metainformation Object Style Sheet and Target 51 52 XHTML Basic 1 1 replaces the Basic Forms Module with the Forms Module and adds the Intrinsic Events Presentation and Scripting modules It also supports additional tags and attributes from other modules This version became a W3C recommendation on 29 July 2008 53 The current version of XHTML Basic is 1 1 Second Edition 23 November 2010 in which the language is re implemented in the W3C s XML Schema language This version also supports the lang attribute 54 XHTML Print Edit XHTML Print which became a W3C Recommendation in September 2006 is a specialized version of XHTML Basic designed for documents printed from information appliances to low end printers 55 XHTML Mobile Profile Edit Main article XHTML Mobile Profile XHTML Mobile Profile abbreviated XHTML MP or XHTML MP is a third party variant of the W3C s XHTML Basic specification Like XHTML Basic XHTML was developed for information appliances with limited system resources In October 2001 a limited company called the Wireless Application Protocol Forum began adapting XHTML Basic for WAP 2 0 the second major version of the Wireless Application Protocol WAP Forum based their DTD on the W3C s Modularization of XHTML incorporating the same modules the W3C used in XHTML Basic 1 0 except for the Target Module Starting with this foundation the WAP Forum replaced the Basic Forms Module with a partial implementation of the Forms Module added partial support for the Legacy and Presentation modules and added full support for the Style Attribute Module In 2002 the WAP Forum has subsumed into the Open Mobile Alliance OMA which continued to develop XHTML Mobile Profile as a component of their OMA Browsing Specification XHTML Mobile Profile 1 1 Edit To this version finalized in 2004 the OMA added partial support for the Scripting Module and partial support for Intrinsic Events XHTML MP 1 1 is part of v2 1 of the OMA Browsing Specification 1 November 2002 56 XHTML Mobile Profile 1 2 Edit This version finalized on 27 February 2007 expands the capabilities of XHTML MP 1 1 with full support for the Forms Module and OMA Text Input Modes XHTML MP 1 2 is part of v2 3 of the OMA Browsing Specification 13 March 2007 56 XHTML Mobile Profile 1 3 Edit XHTML MP 1 3 finalized on 23 September 2008 uses the XHTML Basic 1 1 document type definition which includes the Target Module Events in this version of the specification are updated to DOM Level 3 specifications i e they are platform and language neutral XHTML 1 2 Edit The XHTML 2 Working Group considered the creation of a new language based on XHTML 1 1 57 If XHTML 1 2 was created it would include WAI ARIA and role attributes to better support accessible web applications and improved Semantic Web support through RDFa The inputmode attribute from XHTML Basic 1 1 along with the target attribute for specifying frame targets might also be present The XHTML2 WG had not been chartered to carry out the development of XHTML1 2 Since the W3C announced that it does not intend to recharter the XHTML2 WG 6 and closed the WG in December 2010 this means that XHTML 1 2 proposal would not eventuate XHTML 2 0 Edit Between August 2002 and July 2006 the W3C released eight Working Drafts of XHTML 2 0 a new version of XHTML able to make a clean break from the past by discarding the requirement of backward compatibility This lack of compatibility with XHTML 1 x and HTML 4 caused some early controversy in the web developer community 58 Some parts of the language such as the role and RDFa attributes were subsequently split out of the specification and worked on as separate modules partially to help make the transition from XHTML 1 x to XHTML 2 0 smoother The ninth draft of XHTML 2 0 was expected to appear in 2009 but on 2 July 2009 the W3C decided to let the XHTML2 Working Group charter expire by that year s end effectively halting any further development of the draft into a standard 6 Instead XHTML 2 0 and its related documents were released as W3C Notes in 2010 59 60 New features to have been introduced by XHTML 2 0 included HTML forms were to be replaced by XForms an XML based user input specification allowing forms to be displayed appropriately for different rendering devices HTML frames were to be replaced by XFrames The DOM Events were to be replaced by XML Events which uses the XML Document Object Model A new list element type the nl element type was to be included to specifically designate a list as a navigation list This would have been useful in creating nested menus which are currently created by a wide variety of means like nested unordered lists or nested definition lists Any element was to be able to act as a hyperlink e g lt li href articles html gt Articles lt li gt similar to XLink However XLink itself is not compatible with XHTML due to design differences Any element was to be able to reference alternative media with the src attribute e g lt p src lbridge jpg type image jpeg gt London Bridge lt p gt is the same as lt object src lbridge jpg type image jpeg gt lt p gt London Bridge lt p gt lt object gt The alt attribute of the img element was removed alternative text was to be given in the content of the img element much like the object element e g lt img src hms audacious jpg gt HMS lt span class italic gt Audacious lt span gt lt img gt A single heading element h was added The level of these headings was determined by the depth of the nesting This would have allowed the use of headings to be infinite rather than limiting use to six levels deep The remaining presentational elements i b and tt still allowed in XHTML 1 x even Strict were to be absent from XHTML 2 0 The only somewhat presentational elements remaining were to be sup and sub for superscript and subscript respectively because they have significant non presentational uses and are required by certain languages All other tags were meant to be semantic instead e g strong for strong emphasis while allowing the user agent to control the presentation of elements via CSS e g rendered as boldface text in most visual browsers but possibly rendered with changes of tone in a text to speech reader larger italic font per rules in a user end stylesheet etc The addition of RDF triple with the property and about attributes to facilitate the conversion from XHTML to RDF XML XHTML5 Edit Main article XHTML5 HTML5 grew independently of the W3C through a loose group of browser manufacturers and other interested parties calling themselves the WHATWG or Web Hypertext Application Technology Working Group The key motive of the group was to create a platform for dynamic web applications they considered XHTML 2 0 to be too document centric and not suitable for the creation of internet forum sites or online shops 61 HTML5 has both a regular text html serialization and an XML serialization which is also known as XHTML5 62 The language is more compatible with HTML 4 and XHTML 1 x than XHTML 2 0 due to the decision to keep the existing HTML form elements and events model It adds many new elements not found in XHTML 1 x however such as section and aside tags The XHTML5 language like HTML5 uses a DOCTYPE declaration without a DTD Furthermore the specification deprecates earlier XHTML DTDs by asking the browsers to replace them with one containing only entity definitions for named characters during parsing 62 Semantic content in XHTML EditXHTML RDFa is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well formed XML documents This host language is one of the techniques used to develop Semantic Web content by embedding rich semantic markup Valid XHTML documents EditThis section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed July 2013 Learn how and when to remove this template message An XHTML document that conforms to an XHTML specification is said to be valid Validity assures consistency in document code which in turn eases processing but does not necessarily ensure consistent rendering by browsers A document can be checked for validity with the W3C Markup Validation Service for XHTML5 the Validator nu Living Validator should be used instead In practice many web development programs provide code validation based on the W3C standards Root element Edit The root element of an XHTML document must be html and must contain an xmlns attribute to associate it with the XHTML namespace The namespace URI for XHTML is http www w3 org 1999 xhtml The example tag below additionally features an xml lang attribute to identify the document with a natural language lt html xmlns http www w3 org 1999 xhtml xml lang ar gt DOCTYPEs Edit Main article DOCTYPE In order to validate an XHTML document a Document Type Declaration or DOCTYPE may be used A DOCTYPE declares to the browser the Document Type Definition DTD to which the document conforms A Document Type Declaration should be placed before the root element The system identifier part of the DOCTYPE which in these examples is the URL that begins with http need only point to a copy of the DTD to use if the validator cannot locate one based on the public identifier the other quoted string It does not need to be the specific URL that is in these examples in fact authors are encouraged to use local copies of the DTD files when possible The public identifier however must be character for character the same as in the examples XML declaration Edit See also Processing Instruction A character encoding may be specified at the beginning of an XHTML document in the XML declaration when the document is served using the application xhtml xml MIME type If an XML document lacks encoding specification an XML parser assumes that the encoding is UTF 8 or UTF 16 unless the encoding has already been determined by a higher protocol For example span class cp lt xml version 1 0 encoding UTF 8 gt span The declaration may be optionally omitted because it declares its encoding the default encoding However if the document instead makes use of XML 1 1 or another character encoding a declaration is necessary Internet Explorer prior to version 7 enters quirks mode if it encounters an XML declaration in a document served as text html Backward compatibility EditXHTML 1 x documents are mostly backward compatible with HTML 4 user agents when the appropriate guidelines are followed XHTML 1 1 is essentially compatible although the elements for ruby annotation are not part of the HTML 4 specification and thus generally ignored by HTML 4 browsers Later XHTML 1 x modules such as those for the role attribute RDFa and WAI ARIA degrade gracefully in a similar manner XHTML 2 0 is significantly less compatible although this can be mitigated to some degree through the use of scripting This can be simple one liners such as the use of document createElement to register a new HTML element within Internet Explorer or complete JavaScript frameworks such as the FormFaces implementation of XForms Examples Edit The following are examples of XHTML 1 0 Strict with both having the same visual output The former one follows the HTML Compatibility Guidelines of the XHTML Media Types Note while the latter one breaks backward compatibility but provides cleaner markup 47 Media type recommendation in RFC 2119 terms for the examples Media type Example 1 Example 2application xhtml xml SHOULD SHOULDapplication xml MAY MAYtext xml MAY MAYtext html MAY SHOULD NOTExample 1 lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Strict EN http www w3 org TR xhtml1 DTD xhtml1 strict dtd gt lt html xmlns http www w3 org 1999 xhtml xml lang en lang en gt lt head gt lt meta http equiv Content Type content text html charset utf 8 gt lt title gt XHTML 1 0 Strict Example lt title gt lt script type text javascript gt lt CDATA function loadpdf document getElementById pdf object src http www w3 org TR xhtml1 xhtml1 pdf gt lt script gt lt head gt lt body onload loadpdf gt lt p gt This is an example of an lt abbr title Extensible HyperText Markup Language gt XHTML lt abbr gt 1 0 Strict document lt br gt lt img id validation icon src http www w3 org Icons valid xhtml10 alt Valid XHTML 1 0 Strict gt lt br gt lt object id pdf object name pdf object type application pdf data http www w3 org TR xhtml1 xhtml1 pdf width 100 height 500 gt lt object gt lt p gt lt body gt lt html gt Example 2 lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Strict EN http www w3 org TR xhtml1 DTD xhtml1 strict dtd gt lt html xmlns http www w3 org 1999 xhtml xml lang en gt lt head gt lt title gt XHTML 1 0 Strict Example lt title gt lt script type application javascript gt lt CDATA function loadpdf document getElementById pdf object src http www w3 org TR xhtml1 xhtml1 pdf gt lt script gt lt head gt lt body onload loadpdf gt lt p gt This is an example of an lt abbr title Extensible HyperText Markup Language gt XHTML lt abbr gt 1 0 Strict document lt br gt lt img id validation icon src http www w3 org Icons valid xhtml10 alt Valid XHTML 1 0 Strict gt lt br gt lt object id pdf object type application pdf data http www w3 org TR xhtml1 xhtml1 pdf width 100 height 500 gt lt object gt lt p gt lt body gt lt html gt Notes The loadpdf function is actually a workaround for Internet Explorer It can be replaced by adding lt param name src value http www w3 org TR xhtml1 xhtml1 pdf gt within lt object gt The img element does not get a name attribute in the XHTML 1 0 Strict DTD Use id instead Cross compatibility of XHTML and HTML EditHTML5 and XHTML5 serializations are largely inter compatible if adhering to the stricter XHTML5 syntax but there are some cases in which XHTML will not work as valid HTML5 e g processing instructions are deprecated in HTML clarify are treated as comments and close on the first gt whereas they are fully allowed in XML are treated as their own type and close on gt 63 See also EditExtensible User Interface Protocol HTML List of XML and HTML character entity referencesReferences Edit Graff Eliot 7 May 2014 Polyglot Markup A robust profile of the HTML5 vocabulary W3C HTML vs XHTML whatwg org The WHATWG Blog whatwg org a b XHTML 1 0 Specification Section 1 What is XHTML World Wide Web Consortium 2000 01 26 Retrieved 2007 06 16 results of HTML 5 text editor name questions w3 org a b c Frequently Asked Questions FAQ about the future of XHTML w3 org HTML5 Working Draft Section 1 6 HTML vs XHTML World Wide Web Consortium 2011 01 13 Retrieved 2011 02 16 XHTML 1 0 Specification Section 1 1 Why the need for XHTML World Wide Web Consortium 2000 01 26 Retrieved 2007 06 16 Pilgrim Mark How Did We Get Here Dive Into HTML5 diveintohtml5 info Retrieved 2016 06 11 Arjun Ray 1999 10 06 Dropping the Normative Reference to SGML was I D ACTION Retrieved 2008 12 29 However since ISO 8879 does not afford applications the leeway to prohibit internal subsets it follows that the letter of the HTML 4 spec automatically disentitles it to be a conforming SGML application Tina Holmboe 2008 10 06 XHTML Myths and Reality The Developer s Archive Archived from the original on 2017 01 12 Retrieved 2008 12 29 Since the design goals of XML itself partially mirrored those of the original HTML it was logical for work to begin on formulating an XML based markup language Kip Hampton 2001 01 10 Creating Web Utilities Using XML XPath XML com Retrieved 2008 12 29 The problem You want to take advantage of the power and simplicity that XML tools can offer but you face a site full of aging HTML documents The solution Convert your documents to XHTML and put Perl and XML XPath to work Jean Luc David 2004 04 14 Developing Wireless Content using XHTML Mobile XML com Retrieved 2008 12 29 A useful feature of XHTML is that it can be manipulated as XML Extensible Stylesheet Language Templates can be used to transform XHTML into WML or any other proprietary mobile formats Namespaces Crash Course Mozilla Developer Center Archived from the original on 2008 10 02 Retrieved 2008 12 29 It has been a long standing goal of the W3C to make it possible for different types of XML based content to be mixed together in the same XML file For example SVG and MathML might be incorporated directly into an XHTML based scientific document Steven Pemberton 2004 07 21 HTML and XHTML Frequently Answered Questions World Wide Web Consortium Retrieved 2008 12 29 with an XML based HTML other XML languages could include bits of XHTML and XHTML documents could include bits of other markup languages We could also take advantage of the redesign to clean up some of the more untidy parts of HTML and add some new needed functionality like better forms Clark James 1997 12 15 Comparison of SGML and XML World Wide Web Consortium Note Shorthand markup HTML 4 Appendix B Performance Implementation and Design Notes W3C Retrieved 30 September 2011 Case Sensitivity SitePoint Pty Ltd Retrieved 30 September 2011 Wilson Nicholas CSS differences between XHTML and HTML XHTML 1 0 Specification Appendix C HTML Compatibility Guidelines World Wide Web Consortium 2000 01 26 Retrieved 2007 06 16 XHTML Media Types W3C Working Group Note World Wide Web Consortium 2002 08 01 Retrieved 2008 06 12 Meta and Inline Tags that Google Understands Google Search Central Greta de Groat 2002 Perspectives on the Web and Google Monika Henzinger Director of Research Google Journal of Internet Cataloging Vol 5 1 pp 17 28 2002 Early implementations such as Mozilla 0 7 and Opera 6 0 both released in 2001 do not incrementally render XHTML as it is received over the network giving a degraded user experience see the Mozilla Web Author FAQ Later browsers such as Opera 9 0 Safari 3 0 and Firefox 3 0 do not have this issue XHTML media type test results w3 org Chris Wilson 2005 09 15 The lt xml gt prolog strict mode and XHTML in IE Retrieved 2007 06 16 I ve also been reading comments for some time in the IEBlog asking for support for the application xml xhtml MIME type in IE I should say that IE7 will not add support for this MIME type we will of course continue to read XHTML when served as text html presuming it follows the HTML compatibility recommendations Chris Wilson 2005 09 15 The lt xml gt prolog strict mode and XHTML in IE Retrieved 2007 06 16 If we tried to support real XHTML in IE 7 we would have ended up using our existing HTML parser which is focused on compatibility and hacking in XML constructs It is highly unlikely we could support XHTML well in this way in particular we would certainly not detect a few error cases here or there and we would silently support invalid cases This would of course cause compatibility problems based on parser error handling in the future which XML is explicitly trying to avoid we don t want to cause another mess like the one with current HTML error handling rooted in compatibility with earlier browsers you can blame me for that personally somewhat but not IE I would much rather take the time to implement XHTML properly after IE 7 and have it be truly interoperable Hachamovitch Dean 2010 03 16 HTML5 Hardware Accelerated First IE9 Platform Preview Available for Developers IEBlog on Microsoft Developer Network Microsoft Retrieved 2010 03 22 At this time we re looking for developer feedback on our implementation of HTML5 s parsing rules Selection APIs XHTML support and inline SVG Within CSS3 we re looking for developer feedback on IE9 s support for Selectors Namespaces Colors Values Backgrounds and Borders and Fonts List of XHTML Sites the X Philes Retrieved 2008 08 26 In 2007 37 leaders in search engine optimisation concluded that having keywords in the keywords attribute is little to none Sanger nu blog September 9 2008 Retrieved August 2 2011 Archived February 21 2009 at the Wayback Machine Meta used for SEO 18 December 2015 Archived from the original on March 31 2016 Retrieved March 18 2016 Danny Sullivan How To Use HTML Meta Tags Archived 2008 09 13 at the Wayback Machine Search Engine Watch December 5 2002 a b Ian Hickson a former developer of the Opera browser and cofounder of the WHATWG 2002 09 08 Sending XHTML as text html Considered Harmful Retrieved 2007 06 16 Anne van Kesteren a developer of the Opera browser 2004 06 13 XHTML is invalid HTML Retrieved 2007 06 16 Maciej Stachowiak a developer of Apple s Safari browser 2006 09 20 Understanding HTML XML and XHTML Retrieved 2007 06 16 Brad Fults 2005 12 21 Sending XHTML as text HTML Considered Harmful to Feelings Retrieved 2008 09 13 There are not nearly as many disadvantages if any to sending XHTML as text HTML as Ian Hickson claims and the advantages I mentioned above make it well worth using in my humble opinion There are some subtle footnotes and parentheticals in Hickson s article indicating that the harmfulness only applies to authors that don t know the pitfalls of this practice but much like the Do not eat label on the little packets of silica gel Ian s advisory seems to be common sense and not worth mentioning to any author who actually knows what XHTML is and how to write it Paul McDonald 2007 06 30 The case for XHTML Retrieved 2008 09 13 Some people say XHTML on the Web has failed but I say it is our biggest success in the fight for Web Standards XHTML is a good thing for the web though and it s a shame that people are trying to make a case against it To prove this I ll flesh out the myth for you and then show you why XHTML is the best thing since sliced bread when it comes to our fight for Web Standards So to conclude sending XHTML as text html causes no damage or harm anywhere today as long as your XHTML does validate And if you want Web Standards to become more and more widespread stick to using XHTML and validate your pages Tim Berners Lee 2006 10 27 Reinventing HTML Archived from the original on 2007 06 09 Retrieved 2007 06 16 Some things are clearer with the hindsight of several years It is necessary to evolve HTML incrementally The attempt to get the world to switch to XML including quotes around attribute values and slashes in empty tags and namespaces all at once didn t work The large HTML generating public did not move largely because the browsers didn t complain Some large communities did shift and are enjoying the fruits of well formed systems but not all It is important to maintain HTML incrementally as well as continue a transition to a well formed world and develop more power in that world The plan is to charter a completely new HTML group Unlike the previous one this one will be chartered to do incremental improvements to HTML as also in parallel XHTML It will have a different chair and staff contact It will work on HTML and xHTML together We have strong support for this group from many people we have talked to including browser makers Ian Hickson David Hyatt 2011 01 13 HTML5 A vocabulary and associated APIs for HTML and XHTML Retrieved 2011 02 16 Simon Pieters Results of mobile tests Retrieved 2009 10 31 XHTML 1 0 The Extensible HyperText Markup Language W3C Recommendation 26 January 2000 World Wide Web Consortium 2000 01 26 Retrieved 2008 07 19 XHTML 1 0 The Extensible HyperText Markup Language Second Edition World Wide Web Consortium 2002 08 01 Retrieved 2008 07 19 Modularization of XHTML W3C Recommendation 10 April 2001 World Wide Web Consortium 2001 04 10 Retrieved 2008 07 19 XHTML Modularization 1 1 Second Edition W3C Recommendation 29 July 2010 World Wide Web Consortium 2010 07 29 Retrieved 2010 12 31 XHTML 1 1 Module based XHTML W3C Recommendation 31 May 2001 World Wide Web Consortium 2001 05 31 Retrieved 2008 07 19 XHTML Media Types W3C Working Group Note 1 August 2002 World Wide Web Consortium 2002 08 01 Retrieved 2008 07 19 a b XHTML Media Types Second Edition W3C Working Group Note 16 January 2009 World Wide Web Consortium 2009 01 16 Retrieved 2009 01 28 This document supersedes the HTML Compatibility Guidelines originally found in XHTML 1 0 Appendix C XHTML 1 1 XHTML Basic 1 1 XHTML Print Recommendations Revised W3C NEWS ARCHIVE 2010 World Wide Web Consortium Retrieved 12 December 2010 XHTML 1 1 Module based XHTML Second Edition World Wide Web Consortium 2009 05 07 Archived from the original on 2009 05 12 Retrieved 2009 05 25 XHTML Basic W3C Recommendation 19 December 2000 World Wide Web Consortium 2000 12 19 Retrieved 2008 07 19 XHTML Flavors comparisons World Wide Web Consortium 2007 01 09 Retrieved 2013 01 30 XHTML Basic W3 org Retrieved on 2013 07 17 XHTML Basic 1 1 W3 org Retrieved on 2013 07 17 XHTML Basic 1 1 Second Edition w3 org XHTML Print W3C Recommendation 20 September 2006 World Wide Web Consortium 2006 09 20 Retrieved 2008 07 19 a b OMA Browsing Archive OMA Releases Open Mobile Alliance Ltd 26 September 2011 XHTML Agenda 2008 07 09 w3 org See both XHTML 2 0 Considered Harmful and XHTML 2 0 Considered Hopeful by browser developer Tantek Celik who criticizes early drafts of XHTML 2 0 for the absence of the style attribute and the cite element Developer Daniel Glazman offers similar criticism but also shows support for some backward incompatible changes such as the decision to remove the ins and del elements XHTML 2 0 W3C Working Group Note 16 December 2010 World Wide Web Consortium 2010 12 16 Retrieved 2010 12 31 XHTML2 Working Group Documents Published as W3C Notes World Wide Web Consortium 2010 12 16 Retrieved 2010 12 31 Ian Hickson 2008 01 22 HTML 5 1 1 2 Relationship to XHTML2 World Wide Web Consortium Retrieved 2008 07 19 XHTML2 defines a new HTML vocabulary with better features for hyperlinks multimedia content annotating document edits rich metadata declarative interactive forms and describing the semantics of human literary works such as poems and scientific papers However it lacks elements to express the semantics of many of the non document types of content often seen on the Web For instance forum sites auction sites search engines online shops and the like do not fit the document metaphor well and are not covered by XHTML2 This specification aims to extend HTML so that it is also suitable in these contexts a b 9 The XHTML syntax HTML5 w3 org HTML vs XHTML WHATWG WikiExternal links Edit Wikibooks has a book on the topic of XHTML W3C s Markup Home Page XHTML 1 0 Recommendation XHTML 1 1 Recommendation XHTML 2 0 Working Group Note XHTML Basic XHTML 1 0 Strict 1 1 Online Reference Links dealing with the MIME type of XHTML documents Beware of XHTML Sending XHTML as text html Considered Harmful Serving up XHTML with the correct MIME type The Road to XHTML 2 0 MIME Types Mark Pilgrim 3 19 2003 Includes examples for conditionally serving application xhtml xml using PHP Python and Apache via URL rewriting Mozilla Web Author FAQ How is the treatment of application xhtml xml documents different from the treatment of text html documents summarizes one web browser s XHTML processing mode Empty elements in SGML HTML XML and XHTML Heptagrama s Basic XHTML 1 0 Strict Tutorial W3C s Markup Validator HTML to XHTML conversion library for NET Retrieved from https en wikipedia org w index php title XHTML amp oldid 1124411322, wikipedia, wiki, book, books, library,

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