jQuery(document).ready() does not fire
<p>Does anyone know why jQuery document ready might not fire on a website? I put exactly this script in footer and it simply doesn't fire (jQuery 1.8 is included in head section):</p>

<pre><code>&lt;script type="text/javascript"&gt;
jQuery(document).ready(function() { 
     alert('test');
     jQuery("#slideshow iframe").each(function(){ 
          alert('test');
     });
});
&lt;/script&gt;
</code></pre>

<p>There are no Javascript errors, console is empty and when I run this in Firebug's console it works:</p>

<pre><code>jQuery("#slideshow iframe").each(function(){ 
     alert('test');
});
</code></pre>
