I'm mapping new file types in IIS 6 to the ASP.NET processor; for example the .gif image type.
IIS will see a GIF image doesn't not exist (e.g. http://www.example.com/NoExist.GIF ) and raise a 404 HTTP err before passing the request onto ASP.NET. I want to turn off the IIS file check so ASP.NET gets to handle the invalid request how it chooses.