var elem = "TR";

 window.onload = function(){
  if(document.getElementsByTagName){
   var el = document.getElementsByTagName(elem);
    for(var i=0; i<el.length; i++){
      if(el[i].childNodes[0].tagName != "TH"
      && el[i].parentNode.parentNode.className.indexOf("tbl") != -1){
     if(i%2 == 1){
      el[i].className = "off";
      el[i].onmouseout  = function(){
	     this.className = "off";
      }
    } else {
      el[i].className = "on";
      el[i].onmouseout  = function(){
	     this.className = "on";
      }
    }
      el[i].onmouseover = function(){
	     this.className = "hover";
      }
   }
  }
 }
}