function doPopups() {
   if (!document.getElementsByTagName) return false;
   var links=document.getElementsByTagName("a");
   for (var i=0; i < links.length; i++) {
     if (links[i].className.match("popup")) {
       links[i].onclick=function() {
         window.open(this.href, "", "top=40,left=40,width=500,height=500,scrollbars=yes");
         return false;
       }
     }
   }
 }

addLoadEvent(doPopups);