function sfHover() {
	var sfEls = document.getElementById("main_nav").getElementsByTagName("li");
	for (var i=0; i<sfEls.length; i++) {
		sfEls[i].onmouseover=function() {
			this.className = "sfhover";
		}
		sfEls[i].onmouseout=function() {
			this.className = "";
		}
	}
}

addLoadEvent(sfHover);