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.onmouseout=function() {
  this.className=this.className.replace(new RegExp("  sfhover\\b"), " " );
    }
  }
}