function open_win(location)
{
	w = 600;
	h = 400;
	x = (screen.availWidth - w)/2;
	y = (screen.availHeight - h)/2;
	window.open(location, "Announcement", "width=" + w + ",height=" + h + ",status=no,toolbar=no,location=no,menubar=yes,resizable=yes,scrollbars=yes,top="+y+",left="+x);
}