Top Menu Has a space in IE9

I can't find the parameter that handles the float or margin between the main menu item and it's dropdown items. I'm sure this is something that I modfied when I changed the font size, but I can't figure it out now that I noticed there is a space with viewed with IE9. Firefox and Chrome work fine.

add this style block with IE conditional in head section of index.php of template:


<!--[if IE 9]>
<style type="text/css">

#nav > ul {
margin-top:-1px;
}

</style>
<![endif]-->

Thanks for your help.
I tried your suggestion, but it didn't fix. However, the info you provided helped me figure out what to change in the styple sheet.

Thanks again for fantastic support.