message "404, URL Not Found" meaning that the document you've tried to access can't be located.
"Don't bother asking him...he's 404, man".
The first 4 indicates a client error such as a mistyped URL. The middle 0 refers to a general syntax error. The last 4 just indicates the specific error in the group of 40x, which also includes 400: Bad Request, 401: Unauthorized, etc.