You need to do something different in css styling depending on the user having IE, or a specific version of IE. This is common because you may design to web standards, and only need small tweaks to make something work with IE. Use something like this in the HEAD of your page.
<!--[if IE 6]> <style type="text/css"> .yourclassname{your ie 6 specific styling} </style> <![endif]-->
You may also want other conditional things to occur within the page body.
<p><!--[if IE]> According to the conditional comment this is Internet Explorer<br /> <![endif]--> <!--[if IE 5]> According to the conditional comment this is Internet Explorer 5<br /> <![endif]--> <!--[if IE 5.0]> According to the conditional comment this is Internet Explorer 5.0<br /> <![endif]--> <!--[if IE 5.5]> According to the conditional comment this is Internet Explorer 5.5<br /> <![endif]--> <!--[if IE 6]> According to the conditional comment this is Internet Explorer 6<br /> <![endif]--> <!--[if IE 7]> According to the conditional comment this is Internet Explorer 7<br /> <![endif]--> <!--[if gte IE 5]> According to the conditional comment this is Internet Explorer 5 and up<br /> <![endif]--> <!--[if lt IE 6]> According to the conditional comment this is Internet Explorer lower than 6<br /> <![endif]--> <!--[if lte IE 5.5]> According to the conditional comment this is Internet Explorer lower or equal to 5.5<br /> <![endif]--> <!--[if gt IE 6]> According to the conditional comment this is Internet Explorer greater than 6<br /> <![endif]--> </p>