403.18 : “The Specific Request Cannot Be Executed from Current Application Pool.”

403.18 : “The Specific Request Cannot Be Executed from Current Application Pool.”

I came across this issue with one of the customer. He is trying to configure custom error pages. His app architecture is like this... he has a errors folder where he has all the custom error pages. He have many other Virtual Directories and physical directories in the same website. His expectation is to display the custom error pages in the errors directory which is running under an AppPool, say AppPool#1. But his VDs and Ds are running under different AppPools. So 403.18 “The Specific Request Cannot Be Executed from Current Application Pool" is thrown when he is trying to browse an non-existent file in one of his VD which is running under AppPool#2.

There is an article, https://www.microsoft.com/technet/community/columns/insider/iisi0905.mspx#EJD talking about the same error. The Customer followed the article, but didn't solve his problems. The article recommends putting in "IgnoreAppPoolForCustomErrors" DWORD, value 1 under HKLM\SYSTEM\CurrentControlSet\Services\W3SVC. It didn't work! Actually when I tried to put the same "IgnoreAppPoolForCustomErrors" DWORD, value 1 HKLM\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters it worked.

So I guess the right place to put this key is, HKLM\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters

HKLM\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters\IgnoreAppPoolForCustomErrors - DWORD - value 1