When I go to a particular web site, my username and password does not work.

Unless you may be trying to access a page on the Vance.Net site, any other site that asks for a user name and password is specific to that site.  Many sites now require that you sign up with them before you use their site, and it is that name that you choose at that time, or that the site chooses that it is asking for, not your username and password for Vance.Net.  If you are having problems with your username and password for another web site, you must contact someone at that site for more information.