I found this very interesting information..thought I could share..
These lines are taken from the book "Words Words Words" by David Crystal
Everyone logged on to the Internet will have encountered this message sooner or later. A "four-oh-four" error. It tells you that your browser has made a faulty request to a server, typically because a page or site no longer exists. but why 404? The expression derives from the "file not found" message sent out as a response to a faulty enquiry by staff at CERN, in Switzerland - the place where the World Wide Wed was devised. The members of staff worked out of room 404.