function openWindow(URL, width, height) {
  var win;

  if (is_nav4up || is_ie4up) {
    var screenWidth = screen.width;
    var screenHeight = screen.height;
  } else {
    var screenWidth = 640;
    var screenHeight = 480;
  }
  var left = screenWidth / 2 - width / 2;
  var top = screenHeight / 2 - height / 2;

  win = window.open (URL, "openWindow", 'width=' + width +  ',height=' + height + ',toolbar=yes,location=0,left=' + left + ',top=' + top + ',directories=no,resizable=1,scrollbars=yes,menubar=no,status=no' );
}