响应码分五种类型，由它们的第一位数字表示：
1.1xx：信息，请求收到，继续处理
2.2xx：成功，行为被成功地接受、理解和采纳
3.3xx：重定向，为了完成请求，必须进一步执行的动作
4.4xx：客户端错误，请求包含语法错误或者请求无法实现
5.5xx：服务器错误，服务器不能实现一种明显无效的请求
1 Status Code Definitions 2 Informational 1xx 3 100 Continue 4 101 Switching Protocols 5 Successful 2xx 6 200 OK 7 201 Created 8 202 Accepted 9 203 Non-Authoritative Information 10 204 No Content 11 205 Reset Content 12 206 Partial Content 13 Redirection 3xx 14 300 Multiple Choices 15 301 Moved Permanently 16 302 Found 17 303 See Other 18 304 Not Modified 19 305 Use Proxy 20 306 (Unused) 21 307 Temporary Redirect 22 Client Error 4xx 23 400 Bad Request 24 401 Unauthorized 25 402 Payment Required 26 403 Forbidden 27 404 Not Found 28 405 Method Not Allowed 29 406 Not Acceptable 30 407 Proxy Authentication Required 31 408 Request Timeout 32 409 Conflict 33 410 Gone 34 411 Length Required 35 412 Precondition Failed 36 413 Request Entity Too Large 37 414 Request-URI Too Long 38 415 Unsupported Media Type 39 416 Requested Range Not Satisfiable 40 417 Expectation Failed 41 Server Error 5xx 42 500 Internal Server Error 43 501 Not Implemented 44 502 Bad Gateway 45 503 Service Unavailable 46 504 Gateway Timeout 47 505 HTTP Version Not Supported
参考资料：https://tools.ietf.org/html/rfc2616
原文：http://www.cnblogs.com/creasylai19/p/4910135.html