Did you try this one... in web.config

This will be effective for your application only and not all apps hosted in the web server.

Thanks.....

PFA snapshot about how to change it in IIS 7.

This is basically 404 page not found error. you can customize it in two ways

For your Application

Just go to web.config and add following code snippet

You should give valid path of filenotfound.aspx page

For all applications hosted in your web server

Go to IIS and change the error pages.