System error pages
From Joomla! Documentation
Error Page Templates
By default Joomla! uses special templates when it needs to raise an error response. These are located in the templates/system directory. For server-level status codes these are named for the status code that is being raised. The default system error pages are:
- templates/system/403.php (Status code: 403 Forbidden)
- templates/system/404.php (Status code: 404 Not Found)
- templates/system/500.php (Status code: 500 Internal Server Error)
In addition, these system error pages are also available:
- templates/system/component.php (not sure when this is used)
- templates/system/offline.php is used to render the "site is offline" message.
Note that jdoc:include elements are not parsed in these error pages.
The status codes are defined as part of the HTTP protocol in RFC2616. For further information on HTTP status codes see: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
Styling the Error Pages
These pages can be styled using the following CSS classes: