function openPopup(url,w,h) {
  var y = (screen.availHeight - h)/2;
  var x = (screen.availWidth - w)/2;
    
  var parString = "width=" + w + ",height=" + h + ",screenX=" + x + ",screenY=" + y + ",top=" + y + ",left=" + x + ",toolbar=0,location=0,directories=0" + ",status=0,menuBar=0,scrollBars=1,resizable=0";
  window.open(url,"",parString);
}