HTTP 404
Updated: Wikipedia source
In HTTP, the 404 HTTP status code indicates that a web client (i . browser) was able to communicate with a server, but the server could not provide the requested resource. The server may not have the resource or it may not wish to disclose whether it has the resource. The code is often associated with response reason Not Found and is often referred to as page not found or file not found. Often, the server generates a web page for the condition and the client displays it, and often the content indicates the error code. Since the condition is relatively commonly-encountered (i . due to broken or dead links), this code is one of the most recognizable on the World Wide Web.