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);