function wop(u, n, w, h)
{
   var w = window.open(u, n, 'width=' + w + ',height=' + h + ',status=no,menubar=no,resizable=yes,scrollbars=yes,left=' + String((screen.width - w) / 2) + ',top=' + String((screen.height - h) / 2));
   w.focus();
   return w;
}