title: IIS 404 Custom Error not working as expected
body: <p>I'm working on IIS6, ASP.NET, VS2008. The web site uses a custom error handler to catch 404 errors and serve an alternate page. When presented with an url of the form:</p>
  
  <p><strong><a href="http://srv/crimson/articles/index" rel="noreferrer">http://srv/crimson/articles/index</a></strong></p>
  
  <p>Everything works perfectly. But an url of the form:</p>
  
  <p><strong><a href="http://srv/crimson/blog.aspx" rel="noreferrer">http://srv/crimson/blog.aspx</a></strong></p>
  
  <p>Where blog.aspx does not exist, fails with the following message:</p>
  
  <p>Server Error in '/Crimson' Application. Description: HTTP 404... </p>
  
  <p>When I try and debug, none of the breakpoints in my 404 handler are hit. So it appears that something is catching the request earlier. Where? And how to I get it to pass the request on to my handler?</p>
  
  <p><strong>Edit</strong>
  Thanks to those who answered, but none of those ideas worked. I've decided to attack the problem another way.</p>