I have been trying this for a while, but without success. I need
to provide a Custom Access Denied Page for my application. Though I could
achieve this using a custom layout page and a feature, there is an issue, I
am facing. After I applied the custom access denied page, the "Sign in as
Different User" option in the top right menu, started behaving weird.
Whenever I select that option from any page, rather than prompting with
authentication dialog, its redirecting me to the custom access denied page.
This is the first and most important issue.

The next issue is with the master page. The default Access Denied
page is using a simple.master. But I am unable to use that in my custom
access denied page. I am not sure why is it like this.