The core markup language of the World Wide Web

HTML 5 is the next advancement of both HTML 4.01 and XHTML 1.0, as development on the next version of the latter has been ceased. HTML 5 was initially said to become a game-changer in Web application development, making obsolete such plug-in-based rich Internet application (RIA) technologies as Adobe Flash, Microsoft Silverlight, and Sun JavaFX.^[1] Such applications would be made obsolete by specifying a standard video codec for all browsers to use. However, in July 2009, the editor of the burgeoning draft specification dropped the recommendation of the free software Theora and Vorbis codecs, after opposition from Apple and Nokia. This means HTML 5 does not currently specify a common video codec for Web development.
The ideas behind HTML 5, originally referred to as Web Applications 1.0, were pioneered in 2004 by the Web Hypertext Application Technology Working Group (WHATWG); HTML 5 incorporates Web Forms 2.0, another WHATWG specification. The HTML 5 specification was adopted as the starting point of the work of the new HTML working group of the W3C in 2007. The working group published the First Public Working Draft of the specification on January 22, 2008.^[3] The specification is an ongoing work, and is expected to remain so for many years, although parts of HTML 5 are going to be finished and implemented in browsers before the whole specification reaches final Recommendation status. ReadMore >>>

HTML version information (http://www.w3.org)

A valid HTML document declares what version of HTML is used in the document. The document type declaration names the document type definition (DTD) in use for the document (see [ISO8879]).

HTML 4.01 specifies three DTDs, so authors must include one of the following document type declarations in their documents. The DTDs vary in the elements they support.

• The HTML 4.01 Strict DTD includes all elements and attributes that have not been deprecated or do not appear in frameset documents. For documents that use this DTD, use this document type declaration:

• The HTML 4.01 Transitional DTD includes everything in the strict DTD plus deprecated elements and attributes (most of which concern visual presentation). For documents that use this DTD, use this document type declaration:

• The HTML 4.01 Frameset DTD includes everything in the transitional DTD plus frames as well. For documents that use this DTD, use this document type declaration:

HTML V5 and XHTML V2
Two competing standards coexist
(http://www.ibm.com/developerworks/library/x-html5xhtml2.html)

Summary: While the intention of both HTML V5 and XHTML V2 is to improve on the existing versions, the approaches the developers chose to make those improvements is very different. And with differing philosophies come distinct results. For the first time in many years, the direction of upcoming browser versions is uncertain. Uncover the bigger picture behind the details of these two standards.