Error message when you visit a Web site that is hosted on IIS 7.0: "HTTP Error 403.18 – Forbidden"

You have a Web site that is hosted on Internet Information Services (IIS) 7.0. When you try to visit a custom Web page on this Web site, you may receive an error message that resembles the following:

This problem occurs if the custom error page and the Web site are not in the same application pool.

To resolve this problem, make sure that the Web site and the custom error page are in the same application pool.