In prototype with ajax.updater you can chose to show errors in another div than the one you want "real" content in.

Code:
new Ajax.Updater({ success: 'items', failure: 'notice' }, 'ajax_req.php', {
  parameters: { text: $F('text') },
  insertion: Insertion.Bottom
});
But all information i print out from ajax_req.php gets in the items div. How can i print out errors from ajax_req.php into the notice div?