The preview is still in primitive stages: after meddling with it for a while, I could tell that they have a long way to go when it comes to user interface. This seemed to me like a prototype model(I couldn’t even find an address bar!). It still provides a good sneak preview of what we could expect from IE9: a complete reboot.

For one thing, it supports HTML5, the new version of the Hypertext mark-up language that supports more dynamic web pages, geolocation, and video embedding. That becomes apparent when you test things such as the “HTML5 T-Shirt designer,” which uses HTML5 and XHTML to let you paint your own shirt. It definitely reduces the gap of Internet Explorer to its rivals Firefox, Safari, and Chrome in terms of functionality.

Microsoft also focused on adhering to web standards. IE9 scores 55/100 on Acid3 test — a measure of how well a web browser follows certain web standards. Firefox 3.7, for comparison, scores a 97/100, so still far behind. Microsoft also shows off its improved compliance with CSS, including rounded corners. Microsoft also seems intent on being compatible with CSS3, which is currently under development.

In order to bring IE9 into the new era of the web, Microsoft had to sacrifice a few things. The big one: IE9 will not support Windows XP. It could prove to be a smart move, as it might help push more people to upgrade to Windows 7. More importantly, it makes IE9 as web-compliant and advanced as possible.

Microsoft still has a lot to do to win back web users and developers; its market share continues to erode as other browsers with stronger developer ecosystems and more standard-compliant features. This is a strong start though, and a good sign that Microsoft is taking its web browser rivals very seriously.

source: http://www.levoltz.com/2010/03/17/the-new-ie9-more-html5-css3-and-not-for-windows-xp/