function popup( url, w, h ) {
  var id = new Date().getTime();
  var l = (screen.width / 2) - (w / 2);
  var t = (screen.height) / 2 - (h / 2);
  window.open( url, id, 'toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=0,width='+w+',height='+h+',left='+l+',top='+t);
}