function tables(){
var a=document.getElementById("list1");
var trs=a.getElementsByTagName("tr");
for(var i=0;i<trs.length;i++){
    trs[i].onmouseover=function(){this.className="cur";}
   trs[i].onmouseout=function(){this.className="";}
 }
}
window.onload=function(){
tables();
}