title: Change image src for visited link
body: <p>I have a list with several entries.</p>
  
  <pre><code>&lt;ul&gt;    
  &lt;li&gt;
      &lt;a href="http://url" title="The Title"&gt;
      &lt;img src="/badge-unvisited.png" alt="" border="0" /&gt;
      &lt;/a&gt;
  &lt;/li&gt;
  &lt;!-- etc. --&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>I don't want to use jQuery, so it needs to be CSS-only.
  What is the best and easiest way to change the src of the image when it was visited?</p>