The previous version of HTML, HTML 4.01, came in 1999. The web has changed a lot since then.HTML5 is still a work in progress. However, the major browsers support many of the new HTML5 elements and APIs.
Full CSS3 Support
Video and Audio
Local SQL Database
HTML5 is started from cooperation between the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG).
WHATWG was working with web forms and applications, and W3C was working with XHTML 2.0. In 2006, they decided to cooperate and create a new version of HTML.
Reduce the need for external plug-in (like Flash)
Better error handling
More markup to replace scripting
HTML5 should be device independent
The development process should be visible to the public