S 
      visibility="hidden". After the aria-live attribute is added, the child DOM 
      element node with text content has the CSS display property changed to visibility="visible".</p>
    
    <script>  

      function showElement() {
        var node  = document.getElementById('TEST_ID_3');  
        node.setAttribute('style', 'visibility: visible');        
      }

      function addChildElementNode() {
        var node         = document.getElementById('TEST_ID_2');  
        var element_node = doc