XHTML and Accessibility Standards in ASP.NET 2.0 and VS 2005
Stephen Walther has written a great MSDN article on XHTML and Accessibility Standards in ASP.NET 2.0 and VS 2005 that has just been published: http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspp/html/aspnetusstan.asp
The final release of ASP.NET 2.0 now emits XHTML 1.0 Transitional content by default, and VS 2005 also now defaults to validating content markup and providing intellisense/statement completion for both HTML and Javascript using an XHTML 1.0 Transitional schema.
With the Beta2 release, we defaulted to emiting XHTML strict markup but found that it impacted a lot of customer applications with Javascript that depended on the "name" attribute of the <form> tag (for example: script that references elements like "myform.textbox1"). The name attribute is legal in XHTML Transitional, but not allowed in strict, so when we omitted it from rendering with the <form runat=server> tag to be strict we found that a lot of customer applications broke. This is why we ultimately decided to change the default to be XHTML Transitional for the final release.
The good news is that if you do want XHTML strict output, you can still get it with the final release. Just change the new "xhtmlConformance" tag in your web.config file and then ASP.NET will omit markup that complies with the strict standard:
<configuration>
<system.web>
<!--
<xhtmlConformance mode = "Transitional" [Transitional | Legacy | Strict] />
-->
<xhtmlConformance mode="Strict" />
</system.web>
</configuration>
Note that in addition to changing the runtime behavior to be strict, you can also then change the validation drop-down in the VS toolbar to validate html/javascript against XHTML strict as well.
One area where we are still planning to invest a lot more post-Whidbey is with CSS support in both Visual Studio and ASP.NET (with Whidbey we are 100% XHTML standards compliant from a markup perspective, but don't leverage CSS as much as we could). You'll see some of the cool things we are doing with CSS in the new Atlas-based server controls we are releasing in tech-preview form the week of PDC (less than 2 weeks from now), as well as with the preview of the new Visual Web Developer Orcas Edition we are showing in one of the breakout sessions.