title: $(...).tabs is not a function
body: <p>I have this code on two pages on my site, but at one page the function doesn't work. Firebug shows me " $(...).tabs is not a function ". I don't understand why, can anyone tell me what is wrong ?</p>
  
  <p>this is working:
  <a href="http://www.invat-online.net/variante-rezolvate" rel="noreferrer">http://www.invat-online.net/variante-rezolvate</a></p>
  
  <p>this is not working:
  <a href="http://www.invat-online.net/variante-explicate-limba-romana/varianta-01" rel="noreferrer">http://www.invat-online.net/variante-explicate-limba-romana/varianta-01</a></p>
  
  <p>Here is the code:</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;div id="tabss"&gt;
      &lt;ul&gt;
          &lt;li&gt;&lt;a href="#SubiectI"&gt;Subiect I&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="#SubiectII"&gt;Subiect II&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="#SubiectIII"&gt;Subiect III&lt;/a&gt;&lt;/li&gt;
      &lt;/ul&gt;
      &lt;div id="SubiectI"&gt;content here&lt;/div&gt;
      &lt;div id="SubiectII"&gt;content here&lt;/div&gt;
      &lt;div id="SubiectIII"&gt;content here&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <pre class="lang-js prettyprint-override"><code>$(document).ready(function() {
     $("#tabss").tabs();
  });
  </code></pre>