Arghhhh
vanilla drupal 7.14 install, make simple module

<?php
function at_form_alter(&$form, &$form_state, $form_id) {
  if (
$form_id == 'page_node_form') {
   
$form['title']['#prefix'] = '<div id=address-wrapper>';
   
$form['title']['#suffix'] = '</div>';
   
$form['title']['#ajax'] = array(
       
'callback' => '_node_form_callback',
       
'wrapper' => 'address-wrapper',
    );
  }
}

function
_node_form_callback($form, $state) {
  return
$form['title'];
}
?>

what is expected: as title is required field, it should validated to red when you blur from empty title textfield. but
it didn't work:
- ajax works as expected
- on blur ajax performs, i can even make some messages and so on
- but no standart validation

what I'm doing wrong?