ul列表，点击出现下拉菜单

ul列表，点击出现下拉菜单
我要实现的是 鼠标点击li标签，出现它的下级菜单
请问怎么实现？
<%
set rs=Server.CreateObject("ADODB.Recordset")
sql="select * from [BigClass] order by BigClassId asc"
rs.open sql,conn,1,1
%>
<ul class="about" >
    <%
    if not rs.eof then
        i=1
        do while not rs.eof
    %>
        <li id="imgmenu<%=i%>" onClick="showsubmenu(<%=i%>)" style="cursor:hand;"><%=rs("BigClassName")%>
            <ul id="submenu<%=i%>" style="DISPLAY: none">
                <%
                sql="select * from [SmallClass] where BigClassName='"&rs("BigclassName")&"' ORDER BY SmallClassID ASC"
                set rss=server.CreateObject("adodb.recordset")
                rss.open sql,conn,1,1
                if rss.recordcount<>0 then
                do while not rss.eof
                %>
                <li><a href="product_list.asp?SmallClassName=<%=rs("SmallClassName")%>" class="aboutlist"><%=rss("SmallClassName")%></a></li>
                <%
                rss.movenext
                loop
                end if
                rss.close
                set rss = nothing
                %>
            </ul>
        </li>
    <%
              rs.movenext
        loop
    end if
    rs.close
    set rs=nothing
    %>
</ul>