Potentially toughening the competitive landscape for its own Silverlight rich Internet application platform, Microsoft will expand support for the HTML5 specification in its Internet Explorer 9 browser, under a plan revealed Tuesday.

In an announcement at the Mix10 conference in Las Vegas, Microsoft unveiled the Internet Explorer 9 Platform Preview, which features expanded support for the World Wide Web Consortium HTML5 specification as well as hardware-accelerated graphics and text and a new JavaScript engine, known as “chakra.” These efforts will enable developers to use the same markup and deliver graphically and functionally rich Web applications, Microsoft said. The preview is available at Microsoft’s IE test-drive Web site.