sfHover = function() {
    var sfEls = document.getElementById("nav").getElementsByTagName("li")
    for (var i=0; i<sfEls.length; i++) {
        sfEls[i].onmouseover=function() { this.className+=" over" }
        sfEls[i].onmouseout=function() { this.className=this.className.replace(" over", "") }
    }
}
if (window.attachEvent) window.attachEvent("onload", sfHover);