Event.observe( document, 'contentloaded', function(){
  $$('.titulo_pack a').each( 
  	function( v ){
		Event.observe( v, 'click', show_image );
	}
  );
});

function show_image( evt ){
	evt.stop();
	var el = this.parentNode;
	var img = el.search.split('=')[1];
	window.open('/mostrar_foto.php?foto='+img,'ver','width=614,height=415,location=no,toolbar=no,directories=no,menubar=no,resizable=no,scrollbars=no,status=no');
}