Many things that ASP.NET 2.0 developers usually build seem impossible or challenging in a Windows SharePoint Services environment. However with the latest version, Windows SharePoint Services 3.0 architecture is based on ASP.NET 2.0 and therefore enables developers to use virtually all the same techniques that are implemented in ASP.NET 2.0 sites in SharePoint sites.
This Microsoft Office Visual How To demonstrates one of these techniques, using code-behind files within custom content pages.