Yesterday, I thumbed through the C# Docs looking for stuff I might not know yet, and today I am doing the same thing for ASP.NET in hope to fill in some gaps that might help me with a technical interview I have coming up on tuesday.

This is something I did not know, in the web.config you can add a tag to define what level of XHTML compliance to render.

<system.web>
<!-- other elements here -->
    <xhtmlConformance 
        mode="Legacy" />
</system.web>

Where mode could be one of 3 values (taken directly from the MSDN How to page for XHTML Conformance):

Legacy (which is similar to how markup was rendered in previous versions of ASP.NET)

Transitional (XHTML 1.0 Transitional)

Strict (XHTML 1.0 Strict)