function openCenteredWindow(url) {
	parms = 'menubar=no,width=600,height=500,toolbar=no'
	name = "facebook_share"
	height=500
	width=600
   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;
}