title: How to notify screen readers using WAI-ARIA that a div is now visible
body: <p>How do you notify screen readers using WAI-ARIA that a div is now visible?</p>
  
  <p>If we got the html</p>
  
  <pre><code>&lt;div id="foo"&gt;Present main content&lt;/div&gt;
  &lt;div id="bar" style="display: none;"&gt;Hidden content&lt;/div&gt;
  </code></pre>
  
  <p>and then we</p>
  
  <pre><code>$('#foo').hide();
  $('#bar').show();
  </code></pre>
  
  <p>how do we notify screen readers that they should notify the user about the now visible div (or possibly automatically focus on the now visible div)?</p>