setHover = function() {
	var lis = document.getElementById('main_menu').getElementsByTagName('li');
	for ( var i=0; i<lis.length; i++ ) {
		lis[i].onmouseover = function() {
			this.className += " hover";
		}
		lis[i].onmouseout = function() {
			this.className = this.className.replace(new RegExp(" hover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload",setHover);