function openWindow (url, width, height, windowName, featureString)
{
  if (!windowName)
  {
        windowName = '';
  }

  if (!featureString)
  {
        featureString = '';
  }
  else
  {
        featureString = ',' + featureString;
  }

  var x = Math.round((screen.availWidth - width) / 2);
  var y = Math.round((screen.availHeight - height) / 2);

  featureString = 'left=' + x + ',top=' + y + ',width=' + width + ',height=' + height + featureString;

  open (url, windowName, featureString);
}