I want to check if `id` has no content
<p>I want check between id that get in <code>var span</code>, if empty was between it put css for input but it not work. how can fix it?</p>

<pre><code>var span = '#'+$('.valid').closest('.auto_box').find('span').attr('id');
if ($(span+':empty').length != 0) {
    //alert('ok')
    (this).closest('.auto_box').find('input').css('background-color','#000');
}
</code></pre>

<p>See here my full code: <a href="http://jsfiddle.net/Pjqv2/2/" rel="nofollow">http://jsfiddle.net/Pjqv2/2/</a></p>
