title: jquery shake effect and margin-auto
body: <p>Having a spot of bother with this...
  <a href="http://jsfiddle.net/PHPsycho/mwVkm/1/" rel="nofollow">shake effect example</a></p>
  
  <p>in firefox if I omit the line</p>
  
  <pre><code>$this.css({'margin-left':$this.position().left});
  </code></pre>
  
  <p>then the box is animated over to the left instead of in the centre. If I keep that line of code to fix firefox then chrome has the same problem.</p>
  
  <p>Any tips on getting round this would be grand.</p>
  
  <p>thanks in advance</p>