$(document).ready(function (){
    var onHover;
    var activeSelection; 
    $("ul#main_navigation li").bind("mouseenter mouseleave", function(e){
    onHover = this.id;
    $("ul#main_navigation").toggleClass(onHover);
    });     
    activeSelection = ($("ul#main_navigation li").filter(".on").attr("id"));
    $("div#navHolder").addClass(activeSelection);
});