title: javascript getElementsByClassName() always returns none?
body: <p>I want to create the simplest bookmarklet for my browser.</p>
  <pre><code>javascript:document.getElementsByClassName('source').style.visibility='visible';
  </code></pre>
  <p>I have multiple div.source in my body. By default they are set to <code>.source { display:none; }</code> with css.</p>
  <p>My console tells me: <code>Uncaught TypeError: Cannot set property 'display' of undefined</code></p>
  <p>When I click the bookmarklet all .source divs should be visible. What am I doing wrong here?</p>