title: Randomly change a letter in every 60 seconds
body: <p>I am trying to find a method to have a single letter change every 5 seconds.  I have the random part done but cannot work out how to change it every 5 seconds.  Here is what I have put together so far, I am hoping someone can tell me where I am going wrong.</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  &lt;head&gt;
      &lt;script type="text/javascript"&gt;
          function randomString(Length)
          {
              var text = "";
              var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
              for( var i=0; i &lt; Length; i++ )
                  text += possible.charAt(Math.floor(Math.random() * possible.length));
              return text;
          }
          function ChangingRandomString(Length)
          {
              setInterval(function(){
                  return randomString(Length);
              },5000);
          }
      &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="wrap"&gt;
  &lt;p&gt;Random Changing Letter : &lt;script type="text/javascript"&gt;ChangingRandomString(1);&lt;/script&gt;&lt;/p&gt;
  &lt;p&gt;Random Static Letter : &lt;script type="text/javascript"&gt;document.write(randomString(1));&lt;/script&gt;&lt;/p&gt;
  &lt;/div&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>In the ideal world I am looking to also make the changing letter fade in and out as well for those who like a challenge :-) </p>
  
  <p>Thanks in advance for any help.</p>