I've tried setting serverErrorMessageFile to a path relative to machine.config, and to an absolute path, but when accessing an app on our IIS6 server that shares a pool with another ASP.NET version, we still get the big, ugly, red, default Server Application Unavailable message.
Since one of our ASP.NET apps recently (and mysteriously) changed app pools to one occupied by an app with a different ASP.NET version, again (we have yet to determine the cause--patches, third party software, too many admins), we'd like to be able to customize that error so that users see something a bit less alarming and useless if this happens again, for whatever reason.
So, does serverErrorMessageFile not work in IIS6, or does it not work for ASP.NET version conflicts, or have I missed something?