ErrorDocument

The ErrorDocument directive lets you specify what happens when a client asks for a nonexistent document. 

ErrorDocument error-code "document" (in Apache v2)
Server config, virtual host, directory, .htaccess

In the event of a problem or error, Apache can be configured to do one of four things:

  1. Output a simple hardcoded error message.

  2. Output a customized message.

  3. Redirect to a local URL to handle the problem/error.

  4. Redirect to an external URL to handle the problem/error.

The first option is the default, whereas options 2 through 4 are configured using the ErrorDocument directive, which is followed by the HTTP response code and a message or URL. Messages in this context begin with a double quotation mark ("), which does not form part of the message itself. Apache will sometimes offer additional information regarding the problem or error.

URLs can be local URLs beginning with a slash (/ ) or full URLs that the client can resolve. For example: 

ErrorDocument 500 http://foo.example.com/cgi-bin/tester
ErrorDocument 404 /cgi-bin/bad_urls.pl
ErrorDocument 401 /subscription_info.html
ErrorDocument 403 "Sorry can't allow you access today"

Note that when you specify an ErrorDocument that points to a remote URL (i.e., anything with a method such as “http” in front of it), Apache will send a redirect to the client to tell it where to find the document, even if the document ends up being on the same server. This has several implications, the most important being that if you use an ErrorDocument 401 directive, it must refer to a local document. This results from the nature of the HTTP basic authentication scheme.