title: document.getElementById is not working
body: <p>im new to javascript and want to fill a div with some text. but it doesn't work. 
  in the documentation this is the common way to do this. but, why doesn't work this for me?</p>
  
  <p>my code is</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;title&gt;&lt;/title&gt;
  &lt;script type="text/javascript"&gt;
      document.getElementById('mytest').innerHTML="hey";
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;div id="mytest"&gt;&lt;/div&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>