Welcome to WebmasterWorld Guest from 188.8.131.52
Now I'm trying to use custom error documents that do not reside in the sub domain directory itself but in the web root.
Any ideas how I can get this too work?
How about defining the errordocuments as if they existed in the subdomain's root, and then defining the error document as a symbolic link back to the site root directory? This way, you're working using a file-system view instead of a URL view, so you don't need any external redirects (which mess up the HTTP response codes).
Can you use Telnet to log in?
If not, maybe you could create them as files, and ask your host's tech support to change them to symlinks for you. (The only advantage of creating them as files is to act as placeholders for the symlinks so that the techs can see they are in the right directory - might save some back-and-forth with them.)