The newest implementation of HTML being co-developed by the W3C and WHATWG will provide many new capabilities. This new flavor of HTML and the implementation of new tags such as <video>, <audio>, <canvas>, and the integration of Scalable Vector Graphic (SVG) content is some very exciting stuff! The new specification will deprecate several tags and standardize others to help streamline the language and reinforce standards. One of the best improvements is the focus on application programming interfaces (APIs) and the document object model (DOM) as integral pieces instead of afterthoughts.
Apple is pushing HTML5 over Flash to support their decision to disallow the Flash API on their iPhones and iPads. (see Apple – Thoughts on Flash)
However, HTML5 isn’t ready for prime time. The HTML5 specification is still in active development and many browsers don’t fully support it. Based on the latest statistics from 47,847 real-world results recorded since July 10th 2010 by findmebyip.com, there are many supported features on several of the mainstream browsers with Internet Explorer being on the bottom of the list. The newest version of Internet Explorer, IE9, will supposedly resolve those issues. The browser statistics from the end of December 2010 outline that many visitors hoping to see HTML5 in all its glory may be left out.
The remaining 0.6% use a different browser. Of the total Internet Explorer users only 0.5% are on IE9 Beta. (stats from w3schools.com)
In addition to the lack of browser support, the change to HTML5 from XHTML 1.1 or HTML4 could be a fairly significant change as well. It’s always a good idea to do your homework, find out if your target audience will be able to fully experience your site with HTML5 before making the big move to the new specification.