二级连动的另一个不错的实现方法

break;

} 
} 
//--> 
</script>

<table width="400" border="1" cellspacing="0" cellpadding="0" align="center" bordercolordark="#9cc384" bordercolorlight="#FFFFFF"> 
  <tr bgcolor="#E6F0DD" align="center">  
    <td> 
 
      <form method="post" action="a_list.asp" name="send" target="_blank"> 
        <table width="62%" border="0" cellspacing="2" cellpadding="2"> 
          <tr>  
            <td width="44%" align="right">类别：</td> 
            <td width="56%">  
              <table width="95%" border="0" cellspacing="0" cellpadding="0"> 
                <tr>  
                  <td>  
                    <select name="class0" onChange="onselectchange()"> 
                      <option value="2">** 选择一级类别 **</option> 
                      <option value="0">A</option> 
                      <option value="1">B</option> 
                       
                    </select> 
                  </td> 
                </tr> 
                <tr>  
                  <td> </td> 
                </tr> 
                <tr>  
                  <td>  
                    <select name="class1"> 
                      <option value="1">** 选择二级类别 **</option> 
                    </select> 
                  </td> 
                </tr> 
              </table> 
            </td> 
          </tr> 
        </table> 
      </form> 
      
 
      
 
    </td> 
  </tr> 
   
</table>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]