Loading js file for all browsers except IE
As you may be suspected, the original condition is wrong.  Here's a related post on how someone was able to find a better condition for checking the user agent for IE:

https://stackoverflow.com/questions/5302302/php-if-internet-explorer-6-7-8-or-9

summary: use this instead:

if(preg_match('/(?i)msie [1-8]/',$_SERVER['HTTP_USER_AGENT'])){}