HTTP, Hypertext Transfer Protocol, is the method by which clients (i.e. you) and servers communicate. When someone clicks a link, types in a URL or submits out a form, their browser sends a request to a server for information. It might be asking for a page, or sending data, but either way, that is called an HTTP Request. When a server receives that request, it sends back an HTTP Response, with information for the client. Usually, this is invisible, though I’m sure you’ve seen one of the very common Response codes – 404, indicating a page was not found. There are a fair few more status codes sent by servers, and the following is a list of the current ones in HTTP 1.1, along with an explanation of their meanings.
Error Code Range Type of Error Code
100 – 199 Informational Status Codes, rarely used and generally only written to server logs.
200 – 299 Successful, only 200 frequently used – and generally only written to server logs.
300 – 399 Warning , But the request may still be satisfiable.
400 – 499 Client Error, the request is invalid in someway.
500 – 599 Server Error , The server could not fulfil the request.
HTTP Error 101
Continue, This status code is not really an error. This means the request has been completed and rest of the process can continue.
HTTP Error 102
Switching Protocols, This is also not an error. It means When requesting a page, a browser might receive a status code of 101, followed by an “Upgrade” header showing that the server is changing to a different version of HTTP.
HTTP Error 200
OK, This status code means Standard response for HTTP successful requests.
HTTP Error 201
Created, When new pages are created by posted form data or by a CGI process, this is confirmation that it worked.
HTTP Error 202
Accepted, The client request was accepted, through yet not processed.
HTTP Error 203
Non-Authorative Information, Request probably completed successfully but can’t tell from original server.
HTTP Error 204
No Content, Request Completed Successfully but the resource requested is empty.
HTTP Error 205
Reset Content, This allows the server to reset content returned.
HTTP Error 206
Partial Content, The requested file wasn’t downloaded entirely. This is returned when the user presses the stop button before a page is loaded, for example.
HTTP Error 300
Multiple Choices, The requested address refers to more than one file. Depending on how the server is configured, you get an error or a choice of which page you want.
HTTP Error 301
Moved Permanently, The resource is permanently moved to some other place and the response indicates where it is gone.
HTTP Error 302
Moved Temporarily, The resource is temporarily moved to somewhere else and the response indicates where it is present.
HTTP Error 303
See Other / Redirect, An alternative source where should be used at present.
HTTP Error 304
Not Modified, The server has identified from the request information that the client’s copy of information is up-to-date and the requested information does not need to sent again.
HTTP Error 305
Use Proxy, The request must be sent through the indicated proxy server.
HTTP Error 400
Bad Request, The status code of 400 indicates that the server did not understand the request due to bad syntax.
HTTP Error 401
Unauthorized, the status code of 401 indicates that before a resource can be accessed, the client must be authorized by the server.
HTTP Error 402
Payment Required, The 402 status code is not currently in use, being listed as “reserved for future use”.
HTTP Error 403
Forbidden, A 403 status code indicates that the client cannot access the requested resource. That might mean that the wrong username and password were sent in the request, or that the permissions on the server do not allow what was being asked.
HTTP Error 404
Not Found, The requested file was not found on the server. Possibly because it was deleted, or never existed before. Often caused by misspellings of URLs.
HTTP Error 405
Method Not Allowed, The method you are using to access the file is not allowed.
HTTP Error 406
Not Acceptable, The requested file exists but cannot be used as the client system doesn’t understand the format the file is configured for.
HTTP Error 407
Proxy Authentication Required, The 407 status code is very similar to the 401 status code, and means that the client must be authorized by the proxy before the request can proceed.
HTTP Error 408
Request Timeout, The server took longer than its allowed time to process the request. Often caused by heavy net traffic.
HTTP Error 409
Conflicting, Too many concurrent requests for a single file.
HTTP Error 410
Gone, The file is used to be in this position, but is there no longer.
HTTP Error 411
Content Length Required, The 411 status code occurs when a server refuses to process a request because a content length was not specified.
HTTP Error 412
Precondition Failed, A certain configuration is required for process this request, but the client has not set this up.
HTTP Error 413
Request Entity Too Long, The 413 status code indicates that the requested file was too big to process.
HTTP Error 414
Request URI Too Long, The 414 status code indicates that the URL requested by the client was longer than it can process.
HTTP Error 415
Unsupported Media Type, The server does not support the resource type requested. Frequently found when attempting to serve up content which may require a plug-in.
HTTP Error 500
Internal Server Error, A 500 status code indicates that the server encountered something it didn’t expect and was unable to complete the request.
HTTP Error 501
Not Implemented, The 501 status code indicates that the server does not support all that is needed for the request to be completed.
HTTP Error 502
Bad Gateway, The server you’re trying to reach is sending back errors.
HTTP Error 503
Service Unavailable, This status code oftenseen on extremely busy servers, and it indicates that the server was unable to complete the request due to a server overload.
HTTP Error 504
Gateway Timeout, The website you are attempting to access is currently unreachable. This may be due to network outage or the website might be experiencing technical difficulties.
HTTP Error 505
HTTP Version Not Supported, The HTTP protocol you are asking for is not supported.