XHTML Validation Module Checker for ASP.NET 2.0
Josh and Bruusi have a great .NET blog here.
They've recently published a very cool XHTML Validation module for ASP.NET 2.0 that allows you to easily identify and catch any non-XHTML markup with your application. You register it as an ASP.NET HttpModule within your app's web.config file, and then it watches and checks all page output for XHTML compliance:
This makes it much easier to test different user-interaction scenarios that can't be easily verified with online XHTML validators (for example: pages that require someone to login, or which do posts, etc), and provides a really easy way to verify that your markup is standards compliant. You can learn more about the XHTML Validation Module and download it for free here: http://www.thejoyofcode.com/Validator_Module.aspx
To learn more about building XHTML standards compliant sites with ASP.NET 2.0, make sure to also check out Stephen Walther's great article here. You can also download a set of free XHTML and CSS based designer-built templates for ASP.NET 2.0 here (these provide an attractive set of UI templates that were built by a professional designer and which you can easily re-use within your own solutions for free).
Hope this helps,
Scott
P.S. And one more reminder, the ASP.NET 2.0 CSS Control Adapter Toolkit that I mentioned in this upcoming releases post will ship later this month.