<style>
/* all browsers make border red */
#anyelement { border : 2px solid red; }
/* all browsers see this, but only IE thinks #IEroot exists as an element and makes border blue */
#IEroot #anyelement { border-color : blue; }
</style>
<body>
<!--[if IE]>
<div id="IEroot">
<![endif]-->
<p id="IE">This browser is IE.</p>
<p id="notIE">This browser is not IE.</p>
<!--[if IE]>
</div>
<![endif]-->
</body>