203 Non-Authoritative Information

   The returned metainformation in the entity-header is not the
   definitive set as available from the origin server, but is gathered
   from a local or a third-party copy. The set presented MAY be a subset
   or superset of the original version. For example, including local
   annotation information about the resource might result in a superset
   of the metainformation known by the origin server. Use of this
   response code is not required and is only appropriate when the
   response would otherwise be 200 (OK).