sfHover = function() {
  var sfEls = document.getElementById("nav").getElementsByTagName("table");
  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);