title: Animate opacity on hover (jQuery)
body: <p>We have a link:</p>
  
  <pre><code>&lt;a href="#"&gt;
      Some text
      &lt;span style="width: 50px; height: 50px; background: url(image.png); overflow: hidden; opacity: 0;"&gt;&lt;/span&gt;
  &lt;/a&gt;
  </code></pre>
  
  <p>And we want to change opacity of <code>&lt;span&gt;</code> with some animation, when the link is hovered.</p>
  
  <p>How would we do it?</p>