sfHover = function() {
    var sfEls = document.getElementById("header").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);