function popup(uri, width, height, name) {
	name = name || 'popup';
	width = width || 500;
	height = height || 500;
	var width_max = screen.width - 50;
	var height_max = screen.height - 100;
	if (width > width_max) width = width_max;
	if (height > height_max) height = height_max;

	var left = Math.round((screen.width - width) / 2);
	var top = Math.round((screen.height - height) / 2.25);

	var params = 'width=' + width + ',height=' + height + ',left=' + left + ',top=' + top;
	params += ',menubar=no';
	params += ',toolbar=no';
	params += ',location=no';
	params += ',directories=no';
	params += ',status=no';
	params += ',resizable=yes';
	params += ',scrollbars=yes';

	var popup = window.open(uri, name, params);
	if (popup) {
		popup.focus();
		return false;
	} else {
		return true;
	}
}