From: Rich Bowen ErrorDocument 401 directive, then it must refer to a local
document.
Microsoft Internet Explorer (MSIE) will by default ignore - server-generated error messages when they are "too small" and substitute - its own "friendly" error messages. The size threshold varies depending on - the type of error, but in general, if you make your error document - greater than 512 bytes, then MSIE will show the server-generated - error rather than masking it. More information is available in - Microsoft Knowledge Base article Q294807.
-Although most error messages can be overridden, there are certain
circumstances where the internal messages are used regardless of the
setting of