The XhtmlConformanceSection class provides a way to programmatically access and modify the xhtmlConformance section of a configuration file.
ASP.NET allows you to create Web pages that are compliant with XHTML 1.1 standards. For more information about the XHTML 1.1 standard, see the W3C site. By default, when you are working with browsers that support HTML 4.0 or later, ASP.NET pages and controls render markup that is compatible with the XHTML 1.0 Transitional standard. However, under some circumstances, you might not want ASP.NET to render XHTML markup. This is typically true when you have existing pages that rely on tags or attributes that would ordinarily be prohibited by XHTML.
Notes to Implementers:
Only rendering changes that are likely to break existing applications are reverted to their old behavior. There is no mechanism to revert all changes made to comply with the XHTML specification.