正常情况下我们得到是200，意味着服务器正常的响应了客户端的请求，写ajax就用这个代码判断服务器是不是正常的响应了请求，这个是必不可少的。我们最常见的就是404，这个代码意思是服务器没有找到客户端请求的页面，也就是页面不存在；还有403，服务器禁止访问；500，服务器方面有错误，主要就是程序方面出了错误，如果在写ajax的时候得到了这个响应码，那就赶快去查找程序的错误吧。
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 Timeout"
409, "Conflict"
410, "Gone"
411, "Length Required"
412, "Precondition Failed"
413, "Request Entity Too Large"
414, "Request-URI Too Long"
415, "Unsupported Media Type"
416, "Requested Range Not Suitable"
417, "Expectation Failed"
500, "Internal Server Error"
501, "Not Implemented"
502, "Bad Gateway"
503, "Service Unavailable"
504, "Gateway Timeout"
505, "HTTP Version Not Supported"

俺查过这个。
所以有时遇到404也不能全怪校长。

好贴