This only works for IE browser versions, but it was added by them because they regularly need some help on things that show up fine in other browsers.
Create your template-ie9.css stylesheet and put it in the same css folder. Then you'll need to add it to the head of your site using this code so it's only called in when IE9 is being used...
<!--[if IE 9]>
<link href="/templates/rt_mynxx_j15/css/template_ie9.css" rel="stylesheet" type="text/css" />
<![endif]-->
I haven't tested this yet with IE9, but this is the procedure for adding stylesheets to all other previous IE versions.