The Microsoft Interent Explorer 9 ( IE9 ) Platform Preview is just a wrapper for the Browser Object, so it doesn’t have much UI, but behind that lack of UI is actually quite a few useful tools.
When you first run the IE9 Platform Preview you get a screen that has minimal menus, and a few links to Microsoft HTML demos.
You can browse to a page or website by selecting Page –> Open and then entering the URL you’d like to go to.
To make certain you are viewing the IE9 version of the web page use Debug –> Force IE9 Document Mode.
Where the Internet Explorer 9 Preview really shines is the developer tools, under Debug –> Developer Tools.
These tools offer all sorts of insight in to your HTML ranging from CSS, Script, and HTML syntax compliance issues, to what objects on your web page are slowing the rendering of the page down the most.