Hover = function() {
    var Els = document.getElementById("nav").getElementsByTagName("LI");
    for (var i=0; i<Els.length; i++) {
        Els[i].onmouseover=function() {
            this.className+=" hover";
        }
        Els[i].onmouseout=function() {
            this.className=this.className.replace(new RegExp(" hover\\b"), "");
        }
    }
}

if (window.attachEvent) window.attachEvent("onload", Hover);