I'm sorry, I didn't quite understand your question. Can you rephrase, please
If you're asking about WC3 compliance, many posts on the IE blog on MSDN describe the team's forcus and goals for compliance. Perhaps one of the posts there would answer your question.
I can say that there were changes to the way IE7 handles certain CSS rules and features, especially with strict pages. More information can be found in the blog posts.
Hope this helps...