Lista de codigos de retorno do protocolo http…

Successful
  Client Requests
200 OK
201 Created
202 Accepted
203 Non-Authorative Information
204 No Content
205 Reset Content
206 Partial Content
Client
  Request Redirected
300 Multiple Choices
301 Moved Permanently
302 Moved Temporarily
303 See Other
304 Not Modified
305 Use Proxy
Client
  Request Errors
400 Bad Request
401 Authorization Required
402 Payment Required (not used yet)
403 Forbidden
404 Not Found
405 Method Not Allowed
406 Not Acceptable (encoding)
407 Proxy Authentication Required  
408 Request Timed Out
409 Conflicting Request
410 Gone
411 Content Length Required
412 Precondition Failed
413 Request Entity Too Long
414 Request URI Too Long
415 Unsupported Media Type
Server
  Errors
500 Internal Server Error
501 Not Implemented
502 Bad Gateway  
503 Service Unavailable  
504 Gateway Timeout  
505 HTTP Version Not Supported  

Lista de respostas possiveis quando se liga a um servidor pelo protocolo http.

Quando se usa API’s fornecidas por terceiros é muito importante analisar os headers retornados pelo servidor para o resultado ser o pretendido!