title: Add another class to a div
body: <p>I have a function that checks the age of a form submission and then returns new content in a div depending on their age. Right now I am just using getElementById to replace the HTML content. BUt I think would work better for me if I could also add a class to a div as well. So for example I have.</p>
  
  <pre><code>if (under certain age) {
      document.getElementById('hello').innerHTML = "&lt;p&gt;Good Bye&lt;/p&gt;"; 
      createCookie('age','not13',0)
      return false;
  } else {
      document.getElementById('hello').innerHTML = "&lt;p&gt;Hello&lt;/p&gt;";  
      return true;
  }
  </code></pre>
  
  <p>What I would like to do is have everything in a div and if return false then that div disappears and is replaced with other content. Can I get any ideas on a good way to achieve this with pure JavaScript. I don't want to use jQuery for this particular function.</p>