How to stop IIS7 from handling 404 errors so you can handle them in ASP.NET
IIS7 has lots of places you could look to make this change: you might start off looking to see if it's an advanced option on your application pool, no, so then you try looking at the web site itself and the option .NET Error Pages. That has to be it, surely! So you try every option there Mode=On, Mode=Off, Mode=Remote Only. Nothing works so you consult the help for those items only learn that "Mode" is to "Select a mode for the error pages: On, Off, or Remote Only." You can see now why help writers at Microsoft are so well paid - who would have guessed that Mode = Remote Only sets the Mode to Remote Only!
Now you are really frustrated but luckily you landed on my blog post here where you learned that the true path to 404 happiness is a simple change to your web.config:
<httpErrors errorMode="Detailed" />