I was trying to find an official, authoritative list of HTTP Status Codes but I kept finding lists that weren’t authoritative or complete. So I searched and found my answer in the Apache HTTP Server source code. (2 files attached below)

Contents

57 APACHE HTTP STATUS RESPONSE CODES

Once I compiled the list of Apache recognized HTTP Status Codes, I was dying to see them all in action (i.e. the corresponding ErrorDocument). At first I thought I would have to create a php or perl script emulating each of the 57 HTTP Status Codes, a tedious undertaking I wasn’t about to do. Instead I “asked Apache” by searching the Apache HTTP Documentation for ambiguity sending Status Codes and/or triggering ErrorDocuments with an Apache Directive.
While reading up on mod_alias and the Redirect directive I found:

Syntax: Redirect [status] URL-path URL
The status argument can be used to return other HTTP status codes. Other status codes can be returned by giving the numeric status code as the value of status. If the status is between 300 and 399, the URL argument must be present, otherwise it must be omitted.

1xx Info / Informational

HTTP_INFO - Request received, continuing process. Indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line.

2xx Success / OK

HTTP_SUCCESS - The action was successfully received, understood, and accepted. Indicates that the client’s request was successfully received, understood, and accepted.

3xx Redirect

HTTP_REDIRECT - The client must take additional action to complete the request. Indicates that further action needs to be taken by the user-agent in order to fulfill the request. The action required may be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A user agent should not automatically redirect a request more than 5 times, since such redirections usually indicate an infinite loop.

4xx Client Error

HTTP_CLIENT_ERROR - The request contains bad syntax or cannot be fulfilled. Indicates case where client seems to have erred. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition.

5xx Server Error

HTTP_SERVER_ERROR - The server failed to fulfill an apparently valid request. Indicate cases in which the server is aware that it has erred or is incapable of performing the request. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. User agents should display any included entity to the user. These response codes are applicable to any request method.

Quick Start to triggering ErrorDocuments for each Status Code

Let start with a quick and easy example. Add the following Redirect rules to your htaccess file, then open your browser and goto each url like yoursite.com/e/400. Don’t create an /e/ directory or any files.

Redirect 400 /e/400
Redirect 503 /e/503
Redirect 405 /e/405

Apache ErrorDocument Results
error 503

Automate the ErrorDocument Triggering

The htaccess Redirects

When a Status code is encountered, Apache outputs the Header and the ErrorDocument for that error code. So you can view any Header and the default ErrorDocument, by causing that numerical error code, which is caused by the Status Code.

For instance, if you request a file that doesn’t exist, a 404 Not Found Header is issued and the corresponding ErrorDocument is served with the 404 Not Found Header.

Redirect 100 /e/100
Redirect 101 /e/101
Redirect 102 /e/102
Redirect 200 /e/200
Redirect 201 /e/201
Redirect 202 /e/202
Redirect 203 /e/203
Redirect 204 /e/204
Redirect 205 /e/205
Redirect 206 /e/206
Redirect 207 /e/207
Redirect 300 /e/300 http://www.askapache.com/?s=300 
Redirect 301 /e/301 http://www.askapache.com/?s=301
Redirect 302 /e/302 http://www.askapache.com/?s=302
Redirect 303 /e/303 http://www.askapache.com/?s=303
Redirect 304 /e/304 http://www.askapache.com/?s=304
Redirect 305 /e/305 http://www.askapache.com/?s=305
Redirect 306 /e/306 http://www.askapache.com/?s=306
Redirect 307 /e/307 http://www.askapache.com/?s=307
Redirect 400 /e/400
Redirect 401 /e/401
Redirect 402 /e/402
Redirect 403 /e/403
Redirect 404 /e/404
Redirect 405 /e/405
Redirect 406 /e/406
Redirect 407 /e/407
Redirect 408 /e/408
Redirect 409 /e/409
Redirect 410 /e/410
Redirect 411 /e/411
Redirect 412 /e/412
Redirect 413 /e/413
Redirect 414 /e/414
Redirect 415 /e/415
Redirect 416 /e/416
Redirect 417 /e/417
Redirect 418 /e/418
Redirect 419 /e/419
Redirect 420 /e/420
Redirect 421 /e/421
Redirect 422 /e/422
Redirect 423 /e/423
Redirect 424 /e/424
Redirect 425 /e/425
Redirect 426 /e/426
Redirect 500 /e/500
Redirect 501 /e/501
Redirect 502 /e/502
Redirect 503 /e/503
Redirect 504 /e/504
Redirect 505 /e/505
Redirect 506 /e/506
Redirect 507 /e/507
Redirect 508 /e/508
Redirect 509 /e/509
Redirect 510 /e/510

PHP script that gets and outputs the Headers/Content

Now all I have to do is add 57 Redirect Directives to my htaccess, and then request each of them 1 at a time from my browser to see the result, and use a packet sniffing program like WireShark to see the Headers. Uh, scratch that, that would take way too long!

Instead I hacked up a simple php script using cURL to automate sending GET Requests to each of the 57 Redirect URL-paths. A side benefit of using the php script is that it performs all 57 Requests concurrently and saves each Requests returned headers and content to an output buffer. After all 57 have been queried, the output buffer is flushed to the browser.

<?php
$SITENAME='http://www.askapache.com';
 
$CODES = array(array('100','101','102'),
array('200','201','202','203','204','205','206','207'),
array('300','301','302','303','304','305','306','307'),
array('400','401','402','403','404','405','406','407','408','409','410','411','412','413',
    '414','415','416','417','418','419','420','421','422','423','424','425','426'),
array('500','501','502','503','504','505','506','507','508','509','510'));
 
$TMPSAVETO='/tmp/'.time().'.txt';
 
# if file exists then delete it
if(is_file($TMPSAVETO))unlink($TMPSAVETO);
 
foreach($CODES as $keyd => $res)
{
    foreach($res as $key)
    {
        $ch = curl_init("$SITENAME/e/$key");
        $fp = fopen ($TMPSAVETO, "a");
        curl_setopt ($ch, CURLOPT_FILE, $fp);
        curl_setopt ($ch, CURLOPT_FOLLOWLOCATION ,1);
        curl_setopt ($ch, CURLOPT_HEADER ,1);
        curl_exec ($ch);
        curl_close ($ch);
        fclose ($fp);
    }
}
$OUT='';
ob_start();
header ("Content-Type: text/plain;");
readfile($TMPSAVETO);
$OUT=ob_get_clean();
echo $OUT;
unlink($TMPSAVETO);
exit;
?>

Headers and Content Returned

100 Continue

HTTP/1.1 100 Continue
 
<html><head><title>100 Continue</title></head><body>
<h1>Continue</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

101 Switching Protocols

HTTP/1.1 101 Switching Protocols
 
<html><head><title>101 Switching Protocols</title></head><body>
<h1>Switching Protocols</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

102 Processing

HTTP/1.1 102 Processing
X-Pad: avoid browser bug
 
<html><head><title>102 Processing</title></head><body>
<h1>Processing</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

200 OK

HTTP/1.1 200 OK
 
<html><head><title>200 OK</title></head><body>
<h1>OK</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

201 Created

HTTP/1.1 201 Created
 
<html><head><title>201 Created</title></head><body>
<h1>Created</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

202 Accepted

HTTP/1.1 202 Accepted
 
<html><head><title>202 Accepted</title></head><body>
<h1>Accepted</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

203 Non-Authoritative Information

HTTP/1.1 203 Non-Authoritative Information
 
<html><head><title>203 Non-Authoritative Information</title></head><body>
<h1>Non-Authoritative Information</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

204 No Content

HTTP/1.1 204 No Content
Content-Type: text/plain; charset=UTF-8
 

205 Reset Content

HTTP/1.1 205 Reset Content
 
<html><head><title>205 Reset Content</title></head><body>
<h1>Reset Content</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

206 Partial Content

HTTP/1.1 206 Partial Content
 
<html><head><title>206 Partial Content</title></head><body>
<h1>Partial Content</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

207 Multi-Status

HTTP/1.1 207 Multi-Status
X-Pad: avoid browser bug
 
<html><head><title>207 Multi-Status</title></head><body>
<h1>Multi-Status</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

300 Multiple Choices

HTTP/1.1 300 Multiple Choices
Location: http://www.askapache.com/?s=300
 
<html><head><title>300 Multiple Choices</title></head><body>
<h1>Multiple Choices</h1>

301 Moved Permanently

HTTP/1.1 301 Moved Permanently
Location: http://www.askapache.com/?s=301
 
<html><head><title>301 Moved Permanently</title></head><body>
<h1>Moved Permanently</h1>
<p>The document has moved <a href="http://www.askapache.com/?s=301">here</a>.</p>

302 Found

HTTP/1.1 302 Found
Location: http://www.askapache.com/?s=302
 
<html><head><title>302 Found</title></head><body>
<h1>Found</h1>
<p>The document has moved <a href="http://www.askapache.com/?s=302">here</a>.</p>

303 See Other

HTTP/1.1 303 See Other
Location: http://www.askapache.com/?s=303
 
<html><head><title>303 See Other</title></head><body>
<h1>See Other</h1>
<p>The answer to your request is located <a href="http://www.askapache.com/?s=303">here</a>.</p>

304 Not Modified

HTTP/1.1 304 Not Modified

305 Use Proxy

HTTP/1.1 305 Use Proxy
Location: http://www.askapache.com/?s=305
 
<html><head><title>305 Use Proxy</title></head><body>
<h1>Use Proxy</h1>
<p>This resource is only accessible through the proxy
http://www.askapache.com/?s=305<br />
You will need to configure your client to use that proxy.</p>

306 unused

HTTP/1.1 306 unused
Location: http://www.askapache.com/?s=306
 
<html><head><title>306 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

307 Temporary Redirect

HTTP/1.1 307 Temporary Redirect
Location: http://www.askapache.com/?s=307
 
<html><head><title>307 Temporary Redirect</title></head><body>
<h1>Temporary Redirect</h1>
<p>The document has moved <a href="http://www.askapache.com/?s=307">here</a>.</p>

400 Bad Request

HTTP/1.1 400 Bad Request
Connection: close
 
<html><head><title>400 Bad Request</title></head><body>
<h1>Bad Request</h1>
<p>Your browser sent a request that this server could not understand.<br />
</p>

401 Authorization Required

HTTP/1.1 401 Authorization Required
 
<html><head><title>401 Authorization Required</title></head><body>
<h1>Authorization Required</h1>
<p>This server could not verify that you
are authorized to access the document
requested.  Either you supplied the wrong
credentials (e.g., bad password), or your
browser doesn't understand how to supply
the credentials required.</p>
<p>Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.</p>

402 Payment Required

HTTP/1.1 402 Payment Required
 
<html><head><title>402 Payment Required</title></head><body>
<h1>Payment Required</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

403 Forbidden

HTTP/1.1 403 Forbidden
 
<html><head><title>403 Forbidden</title></head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access /e/403
on this server.</p>
<p>Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.</p>

404 Not Found

HTTP/1.1 404 Not Found
 
<html><head><title>404 Not Found</title></head><body>
<h1>Not Found</h1>
<p>The requested URL /e/404 was not found on this server.</p>

NOTE:
You will most definately want to check out and use the Google 404 Error Page if you run WordPress.

405 Method Not Allowed

HTTP/1.1 405 Method Not Allowed
Allow: TRACE
 
<html><head><title>405 Method Not Allowed</title></head><body>
<h1>Method Not Allowed</h1>
<p>The requested method GET is not allowed for the URL /e/405.</p>

406 Not Acceptable

HTTP/1.1 406 Not Acceptable
 
<html><head><title>406 Not Acceptable</title></head><body>
<h1>Not Acceptable</h1>
<p>An appropriate representation of the requested resource /e/406 could not be found on this server.</p>

407 Proxy Authentication Required

HTTP/1.1 407 Proxy Authentication Required
 
<html><head><title>407 Proxy Authentication Required</title></head><body>
<h1>Proxy Authentication Required</h1>
<p>This server could not verify that you
are authorized to access the document
requested.  Either you supplied the wrong
credentials (e.g., bad password), or your
browser doesn't understand how to supply
the credentials required.</p>

408 Request Time-out

HTTP/1.1 408 Request Time-out
Connection: close
 
<html><head><title>408 Request Time-out</title></head><body>
<h1>Request Time-out</h1>
<p>Server timeout waiting for the HTTP request from the client.</p>

409 Conflict

HTTP/1.1 409 Conflict
 
<html><head><title>409 Conflict</title></head><body>
<h1>Conflict</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

410 Gone

HTTP/1.1 410 Gone
 
<html><head><title>410 Gone</title></head><body>
<h1>Gone</h1>
<p>The requested resource<br />/e/410<br />
is no longer available on this server and there is no forwarding address.
Please remove all references to this resource.</p>

411 Length Required

HTTP/1.1 411 Length Required
Connection: close
 
<html><head><title>411 Length Required</title></head><body>
<h1>Length Required</h1>
<p>A request of the requested method GET requires a valid Content-length.<br />
</p>

412 Precondition Failed

HTTP/1.1 412 Precondition Failed
 
<html><head><title>412 Precondition Failed</title></head><body>
<h1>Precondition Failed</h1>
<p>The precondition on the request for the URL /e/412 evaluated to false.</p>

413 Request Entity Too Large

HTTP/1.1 413 Request Entity Too Large
Connection: close
 
<html><head><title>413 Request Entity Too Large</title></head><body>
<h1>Request Entity Too Large</h1>
The requested resource<br />/e/413<br />
does not allow request data with GET requests, or the amount of data provided in
the request exceeds the capacity limit.

414 Request-URI Too Large

HTTP/1.1 414 Request-URI Too Large
Connection: close
 
<html><head><title>414 Request-URI Too Large</title></head><body>
<h1>Request-URI Too Large</h1>
<p>The requested URL's length exceeds the capacity
limit for this server.<br />
</p>

415 Unsupported Media Type

HTTP/1.1 415 Unsupported Media Type
 
<html><head><title>415 Unsupported Media Type</title></head><body>
<h1>Unsupported Media Type</h1>
<p>The supplied request data is not in a format
acceptable for processing by this resource.</p>

416 Requested Range Not Satisfiable

HTTP/1.1 416 Requested Range Not Satisfiable

417 Expectation Failed

HTTP/1.1 417 Expectation Failed
 
<html><head><title>417 Expectation Failed</title></head><body>
<h1>Expectation Failed</h1>
<p>The expectation given in the Expect request-header
field could not be met by this server.</p>
<p>The client sent&lt;pre&gt;
    Expect: </p>

418 unused

HTTP/1.1 418 unused
 
<html><head><title>418 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

419 unused

HTTP/1.1 419 unused
 
<html><head><title>419 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

420 unused

HTTP/1.1 420 unused
 
<html><head><title>420 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

421 unused

HTTP/1.1 421 unused
 
<html><head><title>421 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

422 Unprocessable Entity

HTTP/1.1 422 Unprocessable Entity
 
<html><head><title>422 Unprocessable Entity</title></head><body>
<h1>Unprocessable Entity</h1>
<p>The server understands the media type of the
request entity, but was unable to process the
contained instructions.</p>

423 Locked

HTTP/1.1 423 Locked
 
<html><head><title>423 Locked</title></head><body>
<h1>Locked</h1>
<p>The requested resource is currently locked.
The lock must be released or proper identification
given before the method can be applied.</p>

424 Failed Dependency

HTTP/1.1 424 Failed Dependency
 
<html><head><title>424 Failed Dependency</title></head><body>
<h1>Failed Dependency</h1>
<p>The method could not be performed on the resource
because the requested action depended on another
action and that other action failed.</p>

425 No code

HTTP/1.1 425 No code
 
<html><head><title>425 No code</title></head><body>
<h1>No code</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

426 Upgrade Required

HTTP/1.1 426 Upgrade Required
 
<html><head><title>426 Upgrade Required</title></head><body>
<h1>Upgrade Required</h1>
<p>The requested resource can only be retrieved
using SSL.  The server is willing to upgrade the current
connection to SSL, but your client doesn't support it.
Either upgrade your client, or try requesting the page
using https://
</p>

500 Internal Server Error

HTTP/1.1 500 Internal Server Error
Connection: close
 
<html><head><title>500 Internal Server Error</title></head><body>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>
<p>Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.</p>

501 Method Not Implemented

HTTP/1.1 501 Method Not Implemented
Allow: TRACE
Connection: close
 
<html><head><title>501 Method Not Implemented</title></head><body>
<h1>Method Not Implemented</h1>
<p>GET to /e/501 not supported.<br />
</p>

502 Bad Gateway

HTTP/1.1 502 Bad Gateway
X-Pad: avoid browser bug
 
<html><head><title>502 Bad Gateway</title></head><body>
<h1>Bad Gateway</h1>
<p>The proxy server received an invalid
response from an upstream server.<br />
</p>

503 Service Temporarily Unavailable

HTTP/1.1 503 Service Temporarily Unavailable
Connection: close
 
<html><head><title>503 Service Temporarily Unavailable</title></head><body>
<h1>Service Temporarily Unavailable</h1>
<p>The server is temporarily unable to service your
request due to maintenance downtime or capacity
problems. Please try again later.</p>

504 Gateway Time-out

HTTP/1.1 504 Gateway Time-out
 
<html><head><title>504 Gateway Time-out</title></head><body>
<h1>Gateway Time-out</h1>
<p>The proxy server did not receive a timely response
from the upstream server.</p>

505 HTTP Version Not Supported

HTTP/1.1 505 HTTP Version Not Supported
 
<html><head><title>505 HTTP Version Not Supported</title></head><body>
<h1>HTTP Version Not Supported</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

506 Variant Also Negotiates

HTTP/1.1 506 Variant Also Negotiates
 
<html><head><title>506 Variant Also Negotiates</title></head><body>
<h1>Variant Also Negotiates</h1>
<p>A variant for the requested resource
&lt;pre&gt;
/e/506
&lt;/pre&gt;
is itself a negotiable resource. This indicates a configuration error.</p>

507 Insufficient Storage

HTTP/1.1 507 Insufficient Storage
 
<html><head><title>507 Insufficient Storage</title></head><body>
<h1>Insufficient Storage</h1>
<p>The method could not be performed on the resource
because the server is unable to store the
representation needed to successfully complete the
request.  There is insufficient free space left in
your storage allocation.</p>

508 unused

HTTP/1.1 508 unused
 
<html><head><title>508 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

509 unused

HTTP/1.1 509 unused
 
<html><head><title>509 unused</title></head><body>
<h1>unused</h1>
<p>The server encountered an internal error or misconfigurationand was unable to complete your request.</p>
<p>Please contact the server administrator, a@s.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.</p>
<p>More information about this error may be available in the server error log.</p>

510 Not Extended

HTTP/1.1 510 Not Extended
X-Pad: avoid browser bug
 
<html><head><title>510 Not Extended</title></head><body>
<h1>Not Extended</h1>
<p>A mandatory extension policy in the request is not
accepted by the server for this resource.</p>

Apache Source Code

httpd.h

From httpd.h

/**
 * The size of the static array in http_protocol.c for storing
 * all of the potential response status-lines (a sparse table).
 * A future version should dynamically generate the apr_table_t at startup.
 */
#define RESPONSE_CODES 57
#define HTTP_CONTINUE                      100
#define HTTP_SWITCHING_PROTOCOLS           101
#define HTTP_PROCESSING                    102
#define HTTP_OK                            200
#define HTTP_CREATED                       201
#define HTTP_ACCEPTED                      202
#define HTTP_NON_AUTHORITATIVE             203
#define HTTP_NO_CONTENT                    204
#define HTTP_RESET_CONTENT                 205
#define HTTP_PARTIAL_CONTENT               206
#define HTTP_MULTI_STATUS                  207
#define HTTP_MULTIPLE_CHOICES              300
#define HTTP_MOVED_PERMANENTLY             301
 
#define HTTP_MOVED_TEMPORARILY             302
#define HTTP_SEE_OTHER                     303
#define HTTP_NOT_MODIFIED                  304
#define HTTP_USE_PROXY                     305
#define HTTP_TEMPORARY_REDIRECT            307
#define HTTP_BAD_REQUEST                   400
#define HTTP_UNAUTHORIZED                  401
#define HTTP_PAYMENT_REQUIRED              402
#define HTTP_FORBIDDEN                     403
#define HTTP_NOT_FOUND                     404
#define HTTP_METHOD_NOT_ALLOWED            405
#define HTTP_NOT_ACCEPTABLE                406
#define HTTP_PROXY_AUTHENTICATION_REQUIRED 407
#define HTTP_REQUEST_TIME_OUT              408
#define HTTP_CONFLICT                      409
#define HTTP_GONE                          410
#define HTTP_LENGTH_REQUIRED               411
#define HTTP_PRECONDITION_FAILED           412
#define HTTP_REQUEST_ENTITY_TOO_LARGE      413
#define HTTP_REQUEST_URI_TOO_LARGE         414
#define HTTP_UNSUPPORTED_MEDIA_TYPE        415
#define HTTP_RANGE_NOT_SATISFIABLE         416
#define HTTP_EXPECTATION_FAILED            417
#define HTTP_UNPROCESSABLE_ENTITY          422
#define HTTP_LOCKED                        423
#define HTTP_FAILED_DEPENDENCY             424
#define HTTP_UPGRADE_REQUIRED              426
#define HTTP_INTERNAL_SERVER_ERROR         500
#define HTTP_NOT_IMPLEMENTED               501
#define HTTP_BAD_GATEWAY                   502
#define HTTP_SERVICE_UNAVAILABLE           503
#define HTTP_GATEWAY_TIME_OUT              504
#define HTTP_VERSION_NOT_SUPPORTED         505
#define HTTP_VARIANT_ALSO_VARIES           506
#define HTTP_INSUFFICIENT_STORAGE          507
#define HTTP_NOT_EXTENDED                  510
 
/** is the status code informational */
#define ap_is_HTTP_INFO(x)         (((x) >= 100)&&((x) < 200))
/** is the status code OK ?*/
#define ap_is_HTTP_SUCCESS(x)      (((x) >= 200)&&((x) < 300))
/** is the status code a redirect */
#define ap_is_HTTP_REDIRECT(x)     (((x) >= 300)&&((x) < 400))
/** is the status code a error (client or server) */
#define ap_is_HTTP_ERROR(x)        (((x) >= 400)&&((x) < 600))
/** is the status code a client error  */
#define ap_is_HTTP_CLIENT_ERROR(x) (((x) >= 400)&&((x) < 500))
/** is the status code a server error  */
#define ap_is_HTTP_SERVER_ERROR(x) (((x) >= 500)&&((x) < 600))
/** is the status code a (potentially) valid response code?  */
#define ap_is_HTTP_VALID_RESPONSE(x) (((x) >= 100)&&((x) < 600))
 
/** should the status code drop the connection */
#define ap_status_drops_connection(x) \\
      (((x) == HTTP_BAD_REQUEST)           || \\
      ((x) == HTTP_REQUEST_TIME_OUT)      || \\
      ((x) == HTTP_LENGTH_REQUIRED)       || \\
      ((x) == HTTP_REQUEST_ENTITY_TOO_LARGE) || \\
      ((x) == HTTP_REQUEST_URI_TOO_LARGE) || \\
      ((x) == HTTP_INTERNAL_SERVER_ERROR) || \\
      ((x) == HTTP_SERVICE_UNAVAILABLE) || \\
      ((x) == HTTP_NOT_IMPLEMENTED))

HTTP_INFO

Is the status code (x) informational?

x >= 100 && x < 200

HTTP_SUCCESS

Is the status code (x) OK?

x >= 200 && x < 300

HTTP_REDIRECT

Is the status code (x) a redirect?

x >= 300 && x < 400

HTTP_ERROR

Is the status code (x) a error (client or server)?

x >= 400 && x < 600

HTTP_CLIENT_ERROR

Is the status code (x) a client error?

x >= 400 && x < 500

HTTP_SERVER_ERROR

Is the status code (x) a server error?

x >= 500 && x < 600

HTTP_VALID_RESPONSE

Is the status code (x) a (potentially) valid response code?

x >= 100 && x < 600

http_protocol.c

From http_protocol.c

/* New Apache routine to map status codes into array indicies
 *  e.g.  100 -> 0,  101 -> 1,  200 -> 2 ...
 * The number of status lines must equal the value of RESPONSE_CODES (httpd.h)
 * and must be listed in order.
 */
 
static const char * status_lines[RESPONSE_CODES] =
#else
static const char * const status_lines[RESPONSE_CODES] =
#endif
{
    "100 Continue",
    "101 Switching Protocols",
    "102 Processing",
#define LEVEL_200  3
    "200 OK",
    "201 Created",
    "202 Accepted",
    "203 Non-Authoritative Information",
    "204 No Content",
    "205 Reset Content",
    "206 Partial Content",
    "207 Multi-Status",
#define LEVEL_300 11
    "300 Multiple Choices",
    "301 Moved Permanently",
    "302 Found",
    "303 See Other",
    "304 Not Modified",
    "305 Use Proxy",
    "306 unused",
    "307 Temporary Redirect",
#define LEVEL_400 19
    "400 Bad Request",
    "401 Authorization Required",
    "402 Payment Required",
    "403 Forbidden",
    "404 Not Found",
    "405 Method Not Allowed",
    "406 Not Acceptable",
    "407 Proxy Authentication Required",
    "408 Request Time-out",
    "409 Conflict",
    "410 Gone",
    "411 Length Required",
    "412 Precondition Failed",
    "413 Request Entity Too Large",
    "414 Request-URI Too Large",
    "415 Unsupported Media Type",
    "416 Requested Range Not Satisfiable",
    "417 Expectation Failed",
    "418 unused",
    "419 unused",
    "420 unused",
    "421 unused",
    "422 Unprocessable Entity",
    "423 Locked",
    "424 Failed Dependency",
    /* This is a hack, but it is required for ap_index_of_response
     * to work with 426.
     */
    "425 No code",
    "426 Upgrade Required",
#define LEVEL_500 46
    "500 Internal Server Error",
    "501 Method Not Implemented",
    "502 Bad Gateway",
    "503 Service Temporarily Unavailable",
    "504 Gateway Time-out",
    "505 HTTP Version Not Supported",
    "506 Variant Also Negotiates",
    "507 Insufficient Storage",
    "508 unused",
    "509 unused",
    "510 Not Extended"
};

Helpful HTTP Links

  1. HTTP specification, Section 10
  2. TLS Upgrade within HTTP specification, Section 4
  3. HTTP Status Code Registry
  4. WebDAV specification, Section 11
  5. IANA registry
  6. Adobe Flash status code definitions (ie 408)
  7. Microsoft Internet Information Server Status Codes and Sub-Codes
  8. httplint
  9. HTTP Headers, brief intro.
  10. Common User-Agent Issues

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