Want XHTML compliant ASP.NET pages? XHTML Web Controls
This has been long coming for the ASP.NET community ... that was one of the few things that irked me about ASP.NET.
You'll want to check out their demos, specifically their Validator demos. If you view source on the page, you'll notice that there is not one stitch of inline javascript code. And every page has a link to the w3c validator, a brave venture indeed.
So if you're a webmonkey, be sure to check out these fantastic controls, they're sure to keep you compliant with the latest web standards.