function openCenteredWindow(url, height, width, name, parms) {

   var left = Math.floor( (screen.width - width) / 2);

   var top = Math.floor( (screen.height - height) / 2);

   var winParms = "top=" + top + ",left=" + left + ",height=" + height + ",width=" + width;

   if (parms) { winParms += "," + parms; }

   var win = window.open(url, name, winParms);

   if (parseInt(navigator.appVersion) >= 4) { win.window.focus(); }

   return win;

}