菜单问题

这是一个网站的二级菜单，我不解的是他的二级菜单是怎么根据一级动态转换的
<div class="ut_head_04a">
     
 
<ul>
    <li class="current">
        <a id="Ut_header1_NavUrl1_Navrp_ctl00_HyperLink1" href="Default.aspx">首页</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl01_HyperLink1" href="InternationLine/TravelHoliday.html">团队旅游</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl02_HyperLink1" href="Freeline/FreeLineList.aspx">自由行</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl03_HyperLink1" href="Cruise/Cruise.aspx">邮轮</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl04_HyperLink1" href="Visa/visa.html">签证办理</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl05_HyperLink1" href="Island/Island.aspx">海岛</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl06_HyperLink1" href="Hotel/HotelSearch.aspx">国际酒店</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl07_HyperLink1" href="Air/AirSearch.aspx">国际机票</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl08_HyperLink1" href="InterationalArticle/GuideBooks.aspx">旅行社区</a></li>
    <li>
        <a id="Ut_header1_NavUrl1_Navrp_ctl09_HyperLink1" href="users/selUser.aspx">会员专区</a></li>
    
  </ul>
 
</div>
<div class="ut_head_04b">
<ul>
    
 
<ul>
 <li class="noline">
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl00_HyperLink1" href="InternationLine/europe.aspx">欧洲旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl01_HyperLink1" href="InternationLine/australia.aspx">澳洲旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl02_HyperLink1" href="InternationLine/africa.aspx">非洲旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl03_HyperLink1" href="InternationLine/american.aspx">美洲旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl04_HyperLink1" href="InternationLine/LineListsbytgid_0_624.html">亚洲旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl05_HyperLink1" href="InternationLine/LineListsbytgid_0_604.html">世界遗产</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl06_HyperLink1" href="InternationLine/LineListsbytgid_0_609.html">深度漫游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl07_HyperLink1" href="InternationLine/IndiaLineList.aspx">印度旅游</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl08_HyperLink1" href="InternationLine/LineAllList.aspx">旅游线路</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl09_HyperLink1" href="ut_infor/silja/silja.html">诗丽雅</a></li>
    <li>
    <a id="Ut_header1_NextNavUrl1_rpGroup_ctl10_HyperLink1" href="EuropeRailway/EurRailp2p.aspx">欧洲火车</a></li>
    
</ul>
</ul>
</div>