XHTML ASP.Net Compliance
I haven't tried this in yet but I found a good article on making the current version of ASP.Net (pre-Whidbey) XHTML compliant: http://www.charon.co.uk/content.aspx?CategoryID=28&ArticleID=53
Here is another: http://www.liquid-internet.co.uk/content/dynamic/pages/series1article1.aspx