Fixing HTTP Protocol Errors
HTTP 400 errors are typically generated when your browser generates a request that the web server can't understand. If your browser is behaving abnormally, it may be sending bad requests to the servers to which you are trying to connect. This problem is almost always due to a defect with your web browser.
HTTP client errors
If you're attempting to access a file or location that requires a username and password, you must have authorization to access the resource. HTTP 401 errors appear when you either entered the wrong user name and password or when your web browser failed to pass your login information to the web server.
Sometimes, your browser will make a well-formed and correct request to a web server. However, this does not guarantee that the web server will fulfill it. The web server will generate an HTTP 403 error if the server determines that you are forbidden from accessing the resource you attempted to locate.
HTTP 404 errors are the most common HTTP errors. 404 errors are generated whenever the server cannot locate the resource that the browser is requesting. This error can be caused by the user entering a URL in incorrectly, a web master moving the content, or the web browser not understanding how to properly find the resource.
If your browser attempts to perform an operation using a method that is disallowed by the server, an HTTP 405 error will be generated. This will prevent the server from completing the operation and allowing your request.
On occasion, the browser and the server will not be able to agree on a method for passing information back and forth. If this occurs, the server will present your browser with an HTTP 406 error. HTTP 406 errors are very rare thanks to the modernization of web server technology.
If the resource that your browser is attempting to access requires authentication through a proxy, the server will generate an HTTP 407 error. This error means that you must re-authenticate with your proxy or contact your system administrator before proceeding.
When servers and clients communicate, the server may send a request to the browser for more information. If the browser fails to respond within a certain time period, the server will generate an HTTP 408 error, which indicates that the browser took too long to give the server the information it needed.
Although this error rarely appears, it is irritating nonetheless. If the browser is overloaded or crashing and unable to allocate resources to fulfill a server request, then an HTTP 409 error will be generated.
If a resource has been moved by a web master, the web master may leave a marker telling the server what the new location of the resource is. Attempts to access the resource via the old location will generate an HTTP 410 error, indicating that the resource still exists in a different location.
Web servers are vulnerable to attacks from large amounts of incoming data. Because of this, HTTP servers require that all requests contain information regarding the length of the request before the request is processed. If the length of the request is not indicated by your browser, the server will generate an HTTP 411 error.
Browsers and servers communicate on the basis of successful evaluations of markers called preconditions. If a precondition evaluates to 'false' on the web server, then the precondition will be considered as failed and an HTTP 412 error will be generated.
In order to prevent attacks via requests with large amounts of data, web servers will place a limit on how large a request it is willing to fulfill. If your browser exceeds this limit, the server will generate an HTTP 413 error and display it to your browser.
If you send a request to a server through where browser where the address of the resource is too long, the server will generate an HTTP 414 error. This error indicates that the URI, or uniform resource identifier, is too long for the server to process.
Browsers attempting to communicate with servers over an unsupported media type are liable to generate HTTP 415 errors. HTTP 415 errors indicate that the server is not able to communicate with the browser via its indicated media type or protocol.
If a browser requests a resource from a server and the server cannot match the specified resource within the range of conditions provided by the browser, the server will generate an HTTP 416 error.
When you send a request to one server, it may pass that request on to other servers. The originating server will attempt to establish a connection with the servers that are further on, and if those servers fail to respond, the originating server will generate an HTTP 417 error.
HTTP server errors
Servers, just like personal computers, can crash and have errors. If a server encounters an internal error while trying to process a request from your browser, it will generate an HTTP 500 error.
Although web servers are expanding in functionality all the time, not all servers can fulfill all requests. If your browser makes a request to a server that requires functionality that the server does not possess, the server will return an HTTP 501 error. This error indicates that the web server you are trying to access has not implemented the technology necessary to process your request.
Servers will occasionally act as gateways or proxies and pass your request on to servers that are located upstream of the one you originally contacted. If the originating server receives an invalid response from the upstream servers, the originating server will generate an HTTP 502 error. This informs your browser that one of the servers that the originating server was trying to contact on the browser's behalf has had an error.
If the server you are requesting resources from is undergoing maintenance or is suffering from capacity issues, the server will generate an HTTP 503 error. This error indicates that the server is unavailable to generate your request due to a technical limitation.
If the server you are requesting a resource from is acting as a proxy or a gateway and does not receive a response from the upstream servers in a given time period, the originating server will generate an HTTP 504 error. This error indicates that the servers upstream from the server your browser originally requested a resource from are not responding in time for the originating server to process the request.
When your browser attempts to use a different version of the hyper text transfer protocol than your server, the server will generate an HTTP 505 error. This error tells your browser that the server and browser are unable to agree on a common version of HTTP to use as a communication standard.
Fixing HTTP errors
Fixing HTTP errors requires some detective work on your part. First, you must identify the HTTP error code and determine if it is a client or a server error. If the HTTP error is a server error, you should contact the administrator of the web resource and inform them of your HTTP error. This will enable the web master of the errant web resource to correct the problem and restore their site.
If the HTTP error is a client error, you should carefully diagnose your own system and your activities on your browser. Did you enter the URL correctly? Are you trying to access a password-protected page and entering the username or password incorrectly? Are you trying to connect to HTTP servers through esoteric means, such as through a proxy or a gateway? All of these activities can lead to HTTP errors.
If you can't correct HTTP errors you're experiencing by changing the way you try to access the website, try accessing the website from a different computer. If the same client HTTP error is generated from a different computer, chances are the problem is actually with the website. However, if the HTTP client error is not present on the alternative computer, you can safely assume that the issue is with your own PC.
You should try reinstalling your browser or trying an alternative browser, such as Mozilla Firefox. Trying alternative browsers can help you pin the HTTP error on a specific piece of software.
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