Well what are you looking to do? Is it e-commerce? How much money do you have to spend. There's a lot that goes into choosing a platform for your site. We kind of need more information.
It really does depend what you're after. Huge site, loads of Database work - ASP.NET and MSSQL (or PHP and MSSQL if you want to be a monkey). Tiny site, a few pictures - XHTML. Its standards compliant and such like. Eitherway you'll want to know XHTML as its what ASP.NET 2.0 pumps out in its pages.