Hello, we are from the future, we come in peace.

Here are some HTTP status codes for you to meditate over:

400 Bad Request

   The 400 (Bad Request) status code indicates that the server cannot or
   will not process the request due to something that is perceived to be
   a client error (e.g., malformed request syntax, invalid request
   message framing, or deceptive request routing).

408 Request Timeout

   The server timed out waiting for the request. According to HTTP
   specifications: "The client did not produce a request within the time
   that the server was prepared to wait. The client MAY repeat the
   request without modifications at any later time."

409 Conflict

   The 409 (Conflict) status code indicates that the request could not
   be completed due to a conflict with the current state of the target
   resource.  This code is used in situations where the user might be
   able to resolve the conflict and resubmit the request.  The server
   SHOULD generate a payload that includes enough information for a user
   to recognize the source of the conflict.

410 Gone

   Indicates that the resource requested is no longer available and will
   not be available again. This should be used when a resource has been
   intentionally removed and the resource should be purged. Upon
   receiving a 410 status code, the client should not request the
   resource in the future. Clients such as search engines should remove
   the resource from their indices.

417 Expectation Failed

   The server cannot meet the requirements of the Expect request-header

418 I'm a teapot (RFC 2324)

   This code should be returned by teapots requested to brew coffee.