You can have the same attribute for different browsers in the same rule by specifying # and _ prefix
.context_bar_form_field
{
height: 15px;/* apply to all browsers */
#height: 15px;/* override for Microsoft Internet Explorer browsers*/
_height: 21px; ;/* override for IE browsers 6.0 and older */
}
<!--[if gt IE 5]>
<style type="text/css" media="screen">
.idonnyCSS{font-size: 1.3em }
/*The above CSS definitions will only be applies to IE versions greater than 5*/
</style>
<![endif]-->
I prefer the first opton for small changes to keep all definitions for the class/selector in one place.
CSS Filters chart describes "Will the browser apply the rule(s)?".
More discussion are in http://24ways.org/2005/avoiding-css-hacks-for-internet-explorer