var newwin;

function doViewer(url)
{

	var screenWidth		=	(screen.width - 520) / 2;
	var screenHeight	=	(screen.height - 300) / 2;


	newwin = window.open(url,"viewer","width=600,height=360,toolbar=no,resizable=yes,scrollbars=yes,status=yes,location=no,directories=no,menubar=no,top="+screenHeight+",left="+screenWidth+"");

	newwin.focus
}