*.AXD and HTTP 404 Errors

With all the AJAX development going on these days, one problem you are bound to hit is the dreaded 'File not found (404)' error when the browser makes a GET request for the WebResource.axd file. The problem here is that the WebResource.axd is a virtual file in that it does not really exist but is processed by a configured HttpHandler. So if you look around on the web, the first suggesstion to resolve this problem is to review the mapping of the AXD extension and to make sure that the 'Check that file exists' checkbox is cleared.

However, you may still continue to have this problem if you use Wildcard Extensions. It turns out, each wildcard extension also has a similar flag which needs to be cleared as well.

Please use caution when turning off this feature because it is meant to be a security measure and should only be used for such 'virtual' files.