Background-position +/- X pixels
<p>How do I offset the <code>background-position</code>, let's say 20px, from its original position?</p>

<p><strong>Like:</strong></p>

<pre><code>$(".selector").animate("slow").css("backgroundPosition", "center -=20px");
</code></pre>

<p>(That obviously doesn't work... But how do I do this??)</p>
