Internet HTTP Status Messages

部分转自：
http://www.btinternet.com/~wildfire/reference/httpstatus/index.htm
当然了，j2ee API 上也有解释，可以随时查阅API

  HTTP Status Messages are errors that web servers and web browsers generate. There are several types:

1XX  Informational 保留
100 Continue
The server has received the beginning of the request and the client should continue.

101 Switching Protocols
Your computer has sent a request to the server to use a different protocol for the connection. The server responds that it is Ok to proceed with the change.

2xx: Successful 表示请求成功地接收
200 OK
The request by your browser succeeded.

201 Created
The request successfully resulted in the creation of an additional resource and the text line should indicate the URL by which it should be known.

202 Accepted
The 202 response is to allow a server to accept a request for some other process without requiring that the connection to the server persist until the process is completed.

203 Non-Authoritative Information
Basically a 200 response, but where returned data may be from another server than the one originally contacted.

204 No Content
Although the request was successful, there is no content to return. This is usually to permit additional input without a change to the user’s view.

205 Reset Content
Although the request was successful, content was not served. The server is awaiting further input from the user before proceeding.

206 Partial Content
This message might occur if a client has a partial copy of content in its cache and requests and update of missing content. This message indicates that the partial request succeeded.

3xx: Redirection 为完成请求客户需进一步细化请求
300 Multiple ChoicesThe requested resource (e.g., a URL) could be one of several. The user will be provided with a list of possible choices, or the server could automatically redirect.

301 Moved PermanentlyThe requested resource has moved to a new URL. A 410 status code is returned if the new address is unavailable or not to be revealed.

302 FoundThe requested resource has moved, but the browser is not automatically redirected. Instead the new URL should be presented to the user.

303 See Other
As with 302, the requested resource has moved, but if the request was a GET request, an automatic redirect by the browser is acceptable.

304 Not Modified
If a client has a partial copy of content in its cache and requests and update, but the document has not been modified since cached, the server responds with a 304 status code and does not send the content to the client. This allows updates of local cache information without fewer HTTP requests.

305 Use Proxy
The requested resource (e.g. web page) must be accessed through the URL of the proxy server in this message.

306 (Unused)
Not in use - Reserved

307 Temporary Redirect
As with 302 and 303, this code is for a moved resource. 303 and 307 were created as unambiguous alternatives to 302. 307 is a temporarily moved resource and thus the same URL should be continued to be used.

4xx: Client Error
400 Bad Request
The server did not understand your request. An improperly typed URL is usually the cause. If not that, there could be a problem with the document itself.

401 Unauthorized
This URL probably requires a username and password. Try submitting them again in case you made an error. If the password doesn't seem to work, contact the site administrator to resolve the problem.

402 Payment Required
This is intended to return acceptable payment options. Not presently used.

[b]403 Forbidden[/b]
You tried to access a URL for which you don't have permission. If you usually can access this document, there might be a problem with the server. If so, contact the site administrator.

404 Not Found
This is probably the most common status code. Your browser cannot locate the document corresponding to the URL you entered. An improperly typed URL is usually the cause. The document may also have been moved. If you cannot find it elsewhere on the site, it may have been permanently removed.

405 Method Not Allowed
You may be attempting to run a script that is not supported. Some ISPs do not allow scripts on their servers, which could result in this status code. For an explanation of methods in HTTP headers see this page of the HTTP/1.1 protocol

406 Not Acceptable
It’s possible you have requested a page that contains files which your browser has indicated to the server that it cannot accept, for example, a multimedia file that your browser cannot process. Your browser sends information about what files it can accept to the server (in the HTTP header) as part of a request. You might check the preferences settings of your browser to see if there are file types it is not accepting.

407 Proxy Authentication Required
There is a proxy server between your client and the server you are requesting the page from that requires a username and password.

408 Request Timeout
The request took longer than allowed to complete. Try the request again. If this error continues to appear, try waiting a few hours before repeating the request

409 ConflictConflicts are likely to occur where an inappropriate alteration of the resource is being attempted.

410 Gone
A 410 status code is returned if the new address is altogether unavailable or the server admin does not want to reveal it.

411 Length Required
Your client did not define the length of the requested content in the request header.

412 Precondition FailedThe header of the request specified information about acceptable files that is not applicable to the requested file.

413 Request Entity Too Large
The content of the request is more than the server can process. The request may have included a message body, which is not always permissible.

414 Request-URL Too Long
Since a POST request allows for an unlimited amount of data to be sent to a server by tagging it on to the request, if the request were converted to a GET request this error could result. Additionally, since a GET request allows for appending of search or form data in the header, the URL created could be longer than acceptable.

415 Unsupported Media TypeThere may have been an error in the MIME type indicated in the request header, i.e., your browser might have requested an image file, when in fact the requested file is an application.

416 Requested Range Not SatisfiableYour browser, which sends information on acceptable file size as part of its request, may have requested a file that does not fit these parameters. See the HTTP protocol for more information.

417 Expectation Failed
The Expect request-header field is used to indicate that particular server behaviors are required by the client. The server could not execute these expectations.



5xx: Server Error
500 Internal Server Error
There is an internal server error on the site you are trying to contact. Unfortunately, there's nothing you can do other than contact the site administrator.

501 Not ImplementedYou’ve asked the server to do something it can't. The server in question may need to be upgraded.

502 Bad Gateway
The server you contacted for a document had to contact another server to obtain it. The server you first contacted received an error from the second server.

503 Service Unavailable
The server you're trying to access is over tasked at the moment and it can't process your request. The server may be down for maintenance, or there may just be too many users on the site at the moment.

504 Gateway TimeoutYour modem or Internet connection has just hung up on you. There are several possible reasons for this. The most likely is that your connection has been inactive longer than allowed (the time limit will usually be set by your ISP). It could also be a server or network problem.

505 HTTP Version Not SupportedYour browser may have made a request using HTTP 1.1, whereas the server you made the request to supports only up to HTTP 1.0. This may occur when a proxy server sends along a request with a different version number.