Theme Menu Problem

/* ================================================================ 
This copyright notice must be kept untouched in the stylesheet at 
all times.

The original version of this script and the associated (x)html
is available at http://www.stunicholls.com/menu/pro_drop_1.html
Copyright (c) 2005-2007 Stu Nicholls. All rights reserved.
This script and the associated (x)html may be modified in any 
way to fit your requirements.
=================================================================== */
stuHover = function() {
   var cssRule;
   var newSelector;
   for (var i = 0; i < document.styleSheets.length; i++)
      for (var x = 0; x < document.styleSheets[i].rules.length ; x++)
         {
         cssRule = document.styleSheets[i].rules[x];
         if (cssRule.selectorText.indexOf("LI:hover") != -1)
         {
             newSelector = cssRule.selectorText.replace(/LI:hover/gi, "LI.iehover");
            document.styleSheets[i].addRule(newSelector , cssRule.style.cssText);
         }
      }
   var getElm = document.getElementById("nav").getElementsByTagName("LI");
   for (var i=0; i<getElm.length; i++) {
      getElm[i].onmouseover=function() {
         this.className+=" iehover";
      }
      getElm[i].onmouseout=function() {
         this.className=this.className.replace(new RegExp(" iehover\\b"), "");
      }
   }
}
if (window.attachEvent) window.attachEvent("onload", stuHover);