Apache’s mod_userdir allows users to view their sites by entering a tilde(~) and their username as the URL on a specific host. For example http://test.cpanel.net/~fred will bring up the user Fred’s domain. The disadvantage of this feature is that any bandwidth usage used by this site will be put on the domain it is accessed under (in this case test.cpanel.net). Mod_userdir protection prevents access to a domain through domain.com/~user. You may however want to disable it on specific virtual hosts (generally shared SSL hosts).