The post Creating different CSS style selector definitions for different browsers (Firefox, Internet Explorer 7 and IE 6.0) with subsequent comments describes that
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 */
}
Alternatively you can use Conditional CSS stylesheets for Internet Explorer
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