1. Insert a conditional comment targeted at versions of Internet Explorer less than 7:
<head> <!—some HTML omitted for brevity --> <!--[if lt IE 7]> <script src="http://ie7-js.googlecode.com/svn/version/2.1(beta3)/IE7.js"> </script> <![endif]--> </head>
Note that the file is hosted externally from your Joomla! website on googlecode.com.
You may find a more recent version of the files you required link from at http://code.google.com/p/ie7-js/.