Making the W3C Validator work with ASP.NET

Step 2 – the important one – requires that you create a folder in the root of the web application called App_Browsers and create a file in that folder called w3cvalidator.browser. The contents of this file are as follows.

App_Browsers file:

<browsers>
<!--  
Browser capability file for the w3c validator  

sample UA: "W3C_Validator/1.305.2.148 libwww-perl/5.803"  
-->
 <browser id="w3cValidator" parentID="default">
   <identification>
     <userAgent match="^W3C_Validator" />
   </identification>

   <capture>
     <userAgent match="^W3C_Validator/(?'version'(?'major'\d+)(?'minor'\.\d+)\w*).*" />
   </capture>

   <capabilities>
     <capability name="browser" value="w3cValidator" />
     <capability name="majorversion" value="${major}" />
     <capability name="minorversion" value="${minor}" />
     <capability name="version" value="${version}" />
     <capability name="w3cdomversion" value="1.0" />
     <capability name="xml" value="true" />
     <capability name="tagWriter" value="System.Web.UI.HtmlTextWriter" />
   </capabilities>
 </browser>
</browsers>

If this file isn’t present, for example, your ASP.NET application’s