function popupCentered(url, width, height) {
	if (screen.width < width) width=screen.width
	if (screen.height< height) height=screen.height
	var left = (screen.width - parseInt(width))/2;
	var top = (screen.height - parseInt(height))/2;
	var settings = 'left='+left+',top='+top+',width='+width+',height='+height+'';
	window.open(url, '', settings);
}