以下是html代码：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD>
<!-- by sundful starting-->
<BODY>
<script language="JavaScript">
var subcat = new Array();
subcat[0] = new Array('中文','英语','英语')
subcat[1] = new Array('中文','法语','法语')
subcat[2] = new Array('英语','中文','中文')
subcat[3] = new Array('法语','中文','中文')
function changeselect1(locationid)
{
document.form1.s2.length = 0; //初始化下拉列表 清空下拉数据
document.form1.s2.options[0] = new Option('==请选择==',''); //给第一个值
for (i=0; i<subcat.length; i++) //legth=20
{
if (subcat[i][0] == locationid) //[0] [1] 第一列 第二列
{document.form1.s2.options[document.form1.s2.length] = new Option(subcat[i][1], subcat[i][2]);} //建立option
//第一次 length=1 因为有==请选择==
//i=9时 length= 10 值有11个 因为从0数起 subcat[i][0] == locationid屏蔽了再写
}
}
</script>
<form name="form1" method="post" runat="server">
二级联动：
<select name="s1" onChange="changeselect1(this.value)">
<option>==请选择==</option>
<option value="中文">中文</option>
<option value="英语">英语</option>
<option value="英语">法语</option>
</select>
<select name="s2">
<option>==请选择==</option>
</select>
</form>
<!-- by sundful ending-->
</BODY>
</HTML>