title: Animate opacity hide / show
body: <p>so, what is the different between:</p>
  
  <p><strong>A)</strong> (work for me)</p>
  
  <pre><code>... .animate({opacity: "show", marginTop: "25"}); ...
  </code></pre>
  
  <p>...</p>
  
  <p><strong>B</strong> (doesn´t work for me)</p>
  
  <pre><code>... .animate({opacity: "1", marginTop: "25"}); ...
  </code></pre>
  
  <p>e.g <a href="http://jsbin.com/iquwuc/6/edit#preview" rel="nofollow">http://jsbin.com/iquwuc/6/edit#preview</a></p>