unordered list inside the tab panel not working

unordered list inside the tab panel not working

My HTML

   
<div id="tabs">
<ul>
<li><a href="#fragment-1"><span>One</span></a></li>
<li><a href="#fragment-2"><span>Two</span></a></li>
<li><a href="#fragment-3"><span>Three</span></a></li>
</ul>
<div id="fragment-1">
      <ul>
            <li> list 1 </li>
            <li> list 2 </li>
            <li> list 3 </li>
            <li> list 4 </li>
      </ul>     
</div>
<div id="fragment-2">
Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.
</div>
<div id="fragment-3">
Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.
</div>
</div>
<script>
$( "#tabs" ).tabs();
</script>


The ul li in


fragment-1 messes up the whole tab widget. 
Searched everywhere but no answer to it. please help.