根据RFC2616,HTTP协议返回状态码分类如下(详情请参考RFC2616文档)
1xx: 信息性——收到请求，继续处理
2xx: 成功性——成功收到、理解并接受行动
3xx: 重定向——必须采取进一步行动来完成请求
4xx: 客户端错误——请求包含错误语法或不能完成
5xx: 服务器错误——服务器没有成功完成显然有效的请求
具体如下:
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1xx: 信息性——收到请求，继续处理
"100" : Continue
"101" : Switching Protocols
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2xx: 成功性——成功收到、理解并接受行动
"200" : OK
"201" : Created
"202" : Accepted
"203" : Non-Authoritative Information
"204" : No Content
"205" : Reset Content
"206" : Partial Content
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3xx: 重定向——必须采取进一步行动来完成请求
"300" : Multiple Choices
"301" : Moved Permanently
"302" : Found
"303" : See Other
"304" : Not Modified
"305" : Use Proxy
"307" : Temporary Redirect
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4xx: 客户端错误——请求包含错误语法或不能完成
"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
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5xx: 服务器错误——服务器没有成功完成显然有效的请求
"500" : Internal Server Error
"501" : Not Implemented
"502" : Bad Gateway
"503" : Service Unavailable
"504" : Gateway Time-out
"505" : HTTP Version not supported
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