Matt Hester created a great screencast which showed how IE8 is going to help with Cascading Style Sheets (CSS) 2.1 and browser interoperability. He also showed how you can get IE 8 to support IE7 standards mode with the following meta tag:
<!-- Use IE7 mode --> <meta http-equiv="X-UA-Compatible" content="IE=7" />
For a better Code Sample take a look here: Defining Document Compatibility
While IE 8 is being designed to work with CSS 21, we are also forward looking to CSS 3.0 and some of the most popular tools. To learn more about compliance check out the white papers here: CSS 2.1 Compliance
In addition the CSS demos, he showed some exciting HTML 5 features, specifically HTML 5's support for hash functionality, which allows some interesting interaction inside your AJAX applications.
You can download beta here:
The full screencast can be found here ( http://edge.technet.com/Media/ScreenCast-Internet-Explorer-8-Beta-1-part-1-Interop-Goodies/)