$(selector).css('width','+=value') doesn't work
<p>css:</p>

<pre><code>#obj { display:block; width:10%; height:30px; background-color:#006600; }
</code></pre>

<p>javascript:</p>

<pre><code>$(document).ready(function() {

$('#obj').css('width','+=10');

});
</code></pre>

<p>html:</p>

<pre><code>&lt;span id="obj"&gt;&lt;/span&gt;
</code></pre>

<p>it won't grow.</p>
