<!--[if (gte IE 6)&(lte IE 8)]>
<script type="text/javascript" src="js/nwmatcher.min.js"></script>
<script type="text/javascript" src="js/selectivizr.js"></script>
<noscript><link rel="stylesheet" href="css/font-awesome.min.css" /></noscript>
<![endif]-->
<link rel="stylesheet" href="css/font-awesome.min.css"/>
<link rel="stylesheet" href="css/font-awesome-ie7.min.css"/>
e.g.
<i class="icon-check icon-4x"></i>