Error page for access attempt to forbidden page

I have a page whose access is limited to specific roles.  When an anonymous user or a user not in the desired role access the page I get a dotnet error page stating:
"This type of page is not served.
Description: The type of page you have requested is not served because it has been explicitly forbidden.     Please review the URL below and make sure that it is spelled correctly. "

How can I catch this and redirect it to a more user friendly error page?

Debugging is turned on right now, developing modules.

nevermind.  custom error pages work fine.