What is XHTML?

XHTML is an acronym for Extensible HyperText Markup Language and is a reformulation of the markup language HTML so that it conforms to XML syntax. It is a suite of current and future document types and modules aimed to extend and ultimately HTML. XHTML is compatible with HTML 4.0 and compatibility with existing HTML user agents is possible by adopting a small set of guidelines.

XHTML is a World Wide Web Consortium (W3C) Recommendation, who oversee the development of XHTML including its semantics and attributes. XHTML 1.0 was recommended by the W3C on 26 January 2000. XHTML 1.1 was recommended by the W3C on 31 May 2001.

Wikipedia uses XHTML 1.0The original XHTML W3C Recommendation, XHTML 1.0, was simply a reformulation of HTML 4.01 in XML. There are three different “DTDs” of XHTML 1.0, each equal in scope to their respective HTML 4.01 versions.

• XHTML 1.0 Strict is the same as HTML 4.01 Strict, but follows XML syntax rules.

• XHTML 1.0 Transitional is the same as HTML 4.01 Transitional, but follows XML syntax rules. It supports everything found in XHTML 1.0 Strict, but also permits the use of a number of elements and attributes that are judged presentational, in order to ease the transition from HTML 3.2 and earlier. These include <center>, <u>, <strike>, and <applet>. 1)

• XHTML 1.0 Frameset: is the same as HTML 4.01 Frameset, but follows XML syntax rules. It allows the defining of an HTML frameset, a common practice in versions of HTML prior to HTML 4.

Work on XHTML 2.0 is, as of 2007, still ongoing. The current XHTML 2.0 Working Draft is controversial because it breaks backward compatibility with all previous versions, and is therefore, in effect, a new markup language created to circumvent (X)HTML‘s limitations rather than being simply a new version. Many issues with compatibility are easily addressed, however, XHTML 2.0 can currently be parsed the same way a user agent would parse XHTML 1.1: via an XML parser and a default CSS document conforming to the current XHTML 2.0 Working Draft.

New features brought into the HTML family of markup languages by XHTML 2.0:

• HTML forms will be replaced by XForms, an XML-based user input specification allowing forms to be displayed appropriately for different rendering devices.

• HTML frames will be replaced by XFrames.

This article or section contains information about scheduled or expected future software. The content may change as the software release approaches and more information becomes available.

The HTML 5 draft defines a parallel XML serialization for HTML5. The XML serialization is called XHTML5. Unlike XHTML 2.0, XHTML5 is compatible with XHTML 1.x.

XHTML Basic: A special “light” version of XHTML for devices that can not support the larger, richer XHTML dialects, intended for use in handhelds and mobile phones. This is the intended replacement for WML and C-HTML.

XHTML Mobile Profile: Based on XHTML Basic, this OMA (Open Mobile Alliance) effort targets hand phones specifically by adding mobile phone-specific elements to XHTML Basic.

XHTML+Voice: XHTML combined with Voice XML to support both visual and voice interactions.

• XHTML documents conform to XML and can therefore be readily viewed, edited, and validated with standard XML tools.
• XMTML documents can be written to operate as well or better than they did before in existing HTML 4-conforming user agents as well as in new, XHTML 1.0 conforming user agents.
• XHTML documents can utilise applications (e.g. scripts and applets) that rely upon either the HTML Document Object Model or the XML Document Object Model.
• As the XHTML suite continues to evolve and developers constantly discover new ways to express ideas through new markup languages, documents conforming to XHTML will be more likely to interoperate within and among various XHTML environments. That is, developments can expect to gain better backward and future compatibility as XHTML is designed to accommodate new elements or extension attributes.
• XHTML is designed with general user agent interoperability in mind, and is therefore more flexible and accommodating to the continual development of alternate ways of accessing the Internet.

• http://en.wikipedia.org/wiki/XHTML
• http://www.xhtml.org/
• http://www.w3schools.com/xhtml/
• http://www.w3.org/TR/xhtml1/