Only showing firefox referrals to IE users

I looked around online for the code to do this but can't seem to find anything. I would like to show firefox referrals to IE users but link units to Firefox/other browsers. Any idea how to do this?

 

With PHP it is easy:

<?php
if(strstr($_SERVER[HTTP_USER_AGENT], "MSIE")){
?>

Firefox ad code here

<?php
}
else {
?>

ad code for other users here

<?php
}
?>

Code (markup):

I don't know about ASP or other languages. Let the others say about these.

 

I was gonna say css, but that will work too and better.