It is an HTTP error code. Thanks for the post again, I am learning something new.
"<abuse> Someone who's clueless. From the World-Wide Web
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".
404 is one of the standard response codes of the telnet
protocol on which the web's HTTP is based."