The web site hosting server will typically generate a “404 Not Found” web page when a user attempts to follow a broken or dead link; hence the 404 error is one of the most recognisable errors encountered on the World Wide Web.

Some of 404 Sub status codes

  • 404.0 – Not found.
  • 404.1 – Site Not Found.
  • 404.2 – ISAPI or CGI restriction.
  • 404.3 – MIME type restriction.
  • 404.4 – No handler configured.
  • 404.5 – Denied by request filtering configuration.
  • 404.6 – Verb denied.
  • 404.7 – File extension denied.
  • 404.8 – Hidden namespace.
  • 404.9 – File attribute hidden.
  • 404.10 – Request header too long.
  • 404.11 – Request contains double escape sequence.
  • 404.12 – Request contains high-bit characters.
  • 404.13 – Content length too large.
  • 404.14 – Request URL too long.
  • 404.15 – Query string too long.
  • 404.16 – DAV request sent to the static file handler.
  • 404.17 – Dynamic content mapped to the static file handler via a wildcard MIME mapping.
  • 404.18 – Query string sequence denied.
  • 404.19 – Denied by filtering rule.
  • 404.20 – Too Many URL Segments.

 

Source : Wikipedia