Bad Request (error code 400): The Web address you entered or the one sent when you clicked a link was incorrect. You should re-enter the address (you may have misspelt it) or, if it's the fault of a Web link, e-mail the site administrator or Webmaster and advise them of the problem.

Unauthorized (401): You may encounter this message if you attempt to access a restricted site which requires a user ID or password. Forbidden (403) is also found on sites with restricted access, such as those sites restricted to educational users.

Not Found (404): Usually means the Web page is no longer available -- either it's been closed or moved to another server.

Internal Error (500): Denotes a fault at the Web site itself.