Status-Code

- 1xx: Informational - Request received, continuing process

- 2xx: Success - The action was successfully received,

        understood, and accepted

- 3xx: Redirection - Further action must be taken in order to

        complete the request

- 4xx: Client Error - The request contains bad syntax or cannot

        be fulfilled

- 5xx: Server Error - The server failed to fulfill an apparently

        valid request

    Status-Code    =    Status-text

            "100"  : Continue

          | "101"  : Switching Protocols

          | "200"  : OK

          | "201"  : Created

          | "202"  : Accepted

          | "203"  : Non-Authoritative Information

          | "204"  : No Content

          | "205"  : Reset Content

          | "206"  : Partial Content

          | "300"  : Multiple Choices

          | "301"  : Moved Permanently

          | "302"  : Found

          | "303"  : See Other

          | "304"  : Not Modified

          | "305"  : Use Proxy

          | "307"  : Temporary Redirect

          | "400"  : Bad Request

          | "401"  : Unauthorized

          | "402"  : Payment Required

          | "403"  : Forbidden

          | "404"  : Not Found

          | "405"  : Method Not Allowed

          | "406"  : Not Acceptable

　　　　　　| "407"  : Proxy Authentication Required

          | "408"  : Request Time-out

          | "409"  : Conflict

          | "410"  : Gone

          | "411"  : Length Required

          | "412"  : Precondition Failed

          | "413"  : Request Entity Too Large

          | "414"  : Request-URI Too Large

          | "415"  : Unsupported Media Type

          | "416"  : Requested range not satisfiable

          | "417"  : Expectation Failed

          | "500"  : Internal Server Error

          | "501"  : Not Implemented

          | "502"  : Bad Gateway

          | "503"  : Service Unavailable

          | "504"  : Gateway Time-out

          | "505"  : HTTP Version not supported

详情：https://tools.ietf.org/html/rfc2616#section-10.1.1