li标签在4层嵌套下点击链接跳转不了页面


<script src="JS/jquery-1.4.2.js" type="text/javascript"></script>    <script type="text/javascript">
      $(function(){
        $('li:has(ul)')
          .click(function(event){
            if (this == event.target) {
              $(this).css('list-style-image',
                (!$(this).children().is(':hidden')) ?
                  'url(images/plus.gif)' : 'url(images/minus.gif)');
              $(this).children().toggle('slow');
            }
            return false;
          })
          .css({cursor:'pointer',
                'list-style-image':'url(images/plus.gif)'})
          .children().hide();
        $('li:not(:has(ul))').css({
          cursor: 'default',
          'list-style-image':'none'
        });
      });
    </script>    <style type="text/css">
        fieldset
        {
            width: 320px;
        }
    </style>
 <fieldset>
            <legend>班级分组</legend>
            <ul>
                <li><a href="Test4.aspx">0000000000000</a> </li>
            </ul>
            <ul>
                <li>一组
                    <ul>
                        <li>刘浩1</li>
                        <li><a href="Test1.aspx">刘浩2</a></li>
                        <li>刘浩3</li>
                        <li>刘浩4</li>
                    </ul>
                </li>
            </ul>
            <ul>
                <li>二组
                    <ul>
                        <li>张三1</li>
                        <li>张三2</li>
                        <li>张三3</li>
                        <li>张三4</li>
                    </ul>
                </li>
            </ul>
        </fieldset>