Is that possible? Without tweaking, ASP.NET is not standards compliant (XHTML at least, HTML 4 output is compliant I think). Hopefully ASP.NET 2 will be though. Semantics is up to the developer though, ASP.NET cannot make semantic code. That is something
a computer would never be able to do (as they are a human invention and only do what they are programmed to - GIGO). If they were intelligent, 'I, Robot' may become reality.
In the "HTML Help" forums I evangelise with W3C ideals. In the ASP.NET forums, I post about how to get ASP.NET to do what you want and comply with spec.