I have my client whose side panel shows correctly on Firefox and Chrome but it doesn't show well on IE.
I have even tried using
<!DOCTYPE HTML>
and
<meta http-equiv="X-UA-Compatible" content="IE=7,9,10" />
but somehow using <meta http-equiv="X-UA-Compatible" content="IE=7,9,10" >
the drop down menu is overlapping the page content.
http://www.cleanenergycentre.com.au/index.php/solarpower/solar-panels
In order to fix the z-index simply add position:relative to the container
and to your template.css add this part of code to fix the width of the li's width into the dropdown