function update_layers(db){
  for (i=0; i<db; i++){
    o=document.getElementById("lid_"+i);
    o.lastChild.style.visibility='hidden';
    o.target='_blank';
    o.onmouseover=new Function("document.getElementById('did_"+i+"').style.visibility='visible';");
    o.onmouseout=new Function("document.getElementById('did_"+i+"').style.visibility='hidden';");
    o.onmousemove=function (e){
      obj=this.lastChild.style;
      if(e==undefined) e=event;
      obj.top=e.clientY+document.body.scrollTop+13+'px';
      obj.left=e.clientX+document.body.scrollLeft+13+'px';
    }
  }
}