This isn't specifically about CSS, but I found this very interesting about Widbey and "web standards":

http://weblogs.asp.net/scottgu/archive/2003/11/25/39620.aspx

Hopefully new controls coming from MS with Widbey will create "valid HTMLmarkup", unlike the current Visual Studio. Throw the calendar control on a page and then view source. It hurts just to look at it.