Adding a viewer Search Engine

I tried that in the beginning, but all the links to the multisearch.php file failed.. such as on this page:

http://www.interactivetools.com/iforum/gforum.cgi?post=85923;search_string=multisearch;t=search_engine#85923

I'd like to learn it myself because I know it will come up again on future websites. Do you know where a working version of the multisearch.php file can be found?

Thanks!! Tina