http://en.wikipedia.org/wiki/404_error
The 404 or Not Found error message is an HTTP standard response code indicating that the client was able to communicate with the server, but the server either could not find the file that was requested, or was unwilling to fulfill the request for it and did not wish to reveal the reason why.

http://www.thinkgeek.com/tshirts/ladies/6792/
If you've ever run across a "403 Forbidden" error on a web site, it means you've either stumbled onto the wrong page, or you've been snooping where you shouldn't be!