This article applies to dedicated/VPS customers only, as the necessary changes are already made on our shared web servers.
You are unable to view detailed ASP.Net 4 errors on the remote machine, even with CustomErrorsMode = "Off" set in your web.config.
By default, Windows 2008 and ASP.Net 4 are installed in "retail" mode for security purposes.
To enable detailed errors to be viewed remotely, you need to edit the machine.config file on your server.
This is usually located in C:\Windows\Microsoft.Net\Framework\Config
Edit the machine.config file, and look for the entry: <deployment retail="true"/>
Change this to: <deployment retail="false"/>
and save the file.
You should now be able to view detailed ASP.Net errors remotely.