function popup (url,w,h) {
	t = (screen.height/2)-(h); 
	l = (screen.width/2)-(w/2);
	wd = window.open (url, '', 'location=no,scrollbars=no,menubar=no,status=no,resizable=no,top='+t+',left='+l+',width='+w+',height='+h);
}