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

if (window.attachEvent) {
  window.attachEvent("onload", sfHover);
}