The Bing 404 Web Page Error Toolkit for PHP is a customizable
PHP application that replaces the default error page on Microsoft
IIS or Apache web servers with Bing search results that are based
on keywords that have been derived from the URL requested by the
user. The toolkit is available as an open source project and is
released under the Microsoft Public License.
Update June 01, 2010: Please note that this
Toolkit has been superceded by the Bing Search Library for
PHP
PHP;Bing