簡単なjsコードはselece二級連動を実現する（推奨）
以下はhtmlコードです。
<!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(' ',' ',' ')
subcat[1] = new Array(' ',' ',' ')
subcat[2] = new Array(' ',' ',' ')
subcat[3] = new Array(' ',' ',' ')
function changeselect1(locationid)
{
document.form1.s2.length = 0; //
document.form1.s2.options[0] = new Option('== ==',''); //
for (i=0; i<subcat.length; i++) //legth=20
{
if (subcat[i][0] == locationid) //[0] [1]
{document.form1.s2.options[document.form1.s2.length] = new Option(subcat[i][1], subcat[i][2]);} // option
// length=1 == ==
//i=9 length= 10 11 0 subcat[i][0] == locationid
}
}
</script>
<form name="form1" method="post" runat="server">
：
<select name="s1" onChange="changeselect1(this.value)">
<option>== ==</option>
<option value=" "> </option>
<option value=" "> </option>
<option value=" "> </option>
</select>
<select name="s2">
<option>== ==</option>
</select>
</form>
<!-- by sundful ending-->
</BODY>
</HTML>