||Usually occurs due to a space in the URL or other malformed URL syntax. Check if the URL is properly URL-encoded.
||The visitor did not present the correct username and/or password to access the file. This error is often returned for an initial request, at which point the browser will prompt the user for a name and password. These values are provided along with a second request for the file, which will succeed if the user entered the correct information. Therefore, the existence of any given 401 error is not necessarily a problem; you may only care about repeated or unexpected errors.
||This code is reserved for future use.
||The server understood the request and has denied access to the file due to the user authentication values provided. This error is different than error 401. Error 401 says that authentication is required but no values were provided. Error 403 says that the values provided were incorrect.
||The file was not found on the server. This is a very common return code.
||Method Not Allowed
||The HTTP method used in making the request is not allowed for the given file. For example, a script could be written to allow accept data via the POST method, not the GET method.
||The server cannot generate a response that satisfies the Accept values provided in the request header.
||Proxy Authentication Required
||This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy.
||The client did not produce a request within the time that the server was prepared to wait (for example, between the time the socket was opened and when the client sent the request). If your web site generates a lot of 408 errors, take a look at the workload on your server.
||The request could not be completed due to a conflict with the current state of the resource.
||The file no longer exists. This is considered a more "permanent" version of error code 404.
||The server requires a content-length header in the request but it was not provided.
||The precondition given in one or more of the request header fields evaluated to "False" when it was tested on the server. This return code allows the client to place preconditions on the current resource metainformation (header field data) and thus prevent the requested method from being applied to a resource other than the one intended.
||Request Entity Too Large
||The server is refusing to process a request because the request entity is larger than the server is willing or able to process. For example, this can happen if a visitor tries to upload a file that is larger than your server is configured to accept.
||Request-URI Too Long
||The URL requested is too long for the server to handle. This might happen if a GET request includes too many query string parameters, or if the values sent are too long. It can also be a sign that someone is attacking your web site by requested a too-long URL in the hope of exploiting a buffer overrun.
||Unsupported Media Type
||The server is refusing to service the request because the actual media type of the resource does not match the type specified in the request, or is incompatible with the HTTP method being used (such as a file upload via PUT).
||Requested Range Not Satisfiable
||A browser (or other user agent) has requested a range (bytes, usually) which cannot be satisfied.
||The expectation given in an Expect request header field could not be met by your server.
||The request is well-formed but the server cannot process it. This is a WebDAV return code; see RFC 2518.
||The source or destination resource is locked. This is a WebDAV return code; see RFC 2518.
||The method depended on another action, and that action failed. This is a WebDAV return code; see RFC 2518.
||The server is advertising the protocols that it supports for upgrading HTTP connections. This return code is defined in RFC 2817.