为何“document.all.subcategoryid.options”会报错？

在Windows 2000 Server 中，为何“document.all.subcategoryid.options”会报错？而在Windows 2000 Professional不会？
系统提示：document.all.subcategoryid.options 不是对象

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我是 win2000 server 测试没有问题呀!!

1<select name="subcategoryid">
2<option>1   
3<option>2   
4<option>3   
5<option>4   
6</option></option></option></option></select>

1<input onclick="alert(document.all.subcategoryid.options.length)" type="button" value="ok"/>

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grand_subcategory_array 这个数组不存在
name=grandcategoryid 的 select 下拉框网页中也不存在
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只要这两级的级联？
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grand_subcategory_id_array页没有定义
我现在把这两个Array定义成和你前面的一样，在添加了一个select
具体array里面的和select自己修改

  1<html>
  2<head>
  3<title> New Document </title>
  4<meta content="EditPlus" name="Generator"/>
  5<meta content="" name="Author"/>
  6<meta content="" name="Keywords"/>
  7<meta content="" name="Description"/>
  8</head>
  9<body>
 10<script language="JavaScript">   
 11<!--   
 12function checksubmit(cform){   
 13if (cform.keyword.value ==''){   
 14alert('请输入检索关键字');   
 15return false;   
 16}   
 17}   
 18//-->   
 19</script>
 20<script language="javascript">   
 21var category_array = new Array('--选择专业名称--','电子信息工程','计算机科学与技术','通信工程','信息管理与信息系统','自动化');   
 22var category_id_array = new Array(' ','电子信息工程','计算机科学与技术','通信工程','信息管理与信息系统','自动化');   
 23var subcategory_array = new Array(new Array('----选择班级----'),new Array('----选择班级----','电子0011','电子0012','电子0112','电子0111','电子9911','电子9912','电子9913'),new Array('----选择班级----','计算0111','计算0112','计算0113','计算0011','计算0012','计算9911','计算9912'),new Array('----选择班级----','计算0013','通信0111','通信0112','通信0011','通信0012','通信9911','通信9912'),new Array('----选择班级----','信息0111','信息0112','信息0011','信息0012','信息0013','信息9911','信息9912'),new Array('----选择班级----','自动0111','自动0112','自动0111','自动0012','自动9912','自动9912'));   
 24var subcategory_id_array = new Array(new Array(0),new Array(0,'电子0011','电子0012','电子0112','电子0111','电子9911','电子9912','电子9913'),new Array(0,'计算0111','计算0112','计算0113','计算0011','计算0012','计算9911','计算9912'),new Array(0,'计算0013','通信0111','通信0112','通信0011','通信0012','通信9911','通信9912'),new Array(0,'信息0111','信息0112','信息0011','信息0012','信息0013','信息9911','信息9912'),new Array(0,'自动0111','自动0112','自动0111','自动0012','自动9912','自动9912'));   
 25var grand_subcategory_id_array = new Array(new Array('----选择班级----'),new Array('----选择班级----','电子0011','电子0012','电子0112','电子0111','电子9911','电子9912','电子9913'),new Array('----选择班级----','计算0111','计算0112','计算0113','计算0011','计算0012','计算9911','计算9912'),new Array('----选择班级----','计算0013','通信0111','通信0112','通信0011','通信0012','通信9911','通信9912'),new Array('----选择班级----','信息0111','信息0112','信息0011','信息0012','信息0013','信息9911','信息9912'),new Array('----选择班级----','自动0111','自动0112','自动0111','自动0012','自动9912','自动9912'));   
 26var grand_subcategory_array = new Array(new Array('----选择班级----'),new Array('----选择班级----','电子0011','电子0012','电子0112','电子0111','电子9911','电子9912','电子9913'),new Array('----选择班级----','计算0111','计算0112','计算0113','计算0011','计算0012','计算9911','计算9912'),new Array('----选择班级----','计算0013','通信0111','通信0112','通信0011','通信0012','通信9911','通信9912'),new Array('----选择班级----','信息0111','信息0112','信息0011','信息0012','信息0013','信息9911','信息9912'),new Array('----选择班级----','自动0111','自动0112','自动0111','自动0012','自动9912','自动9912'));   
 27function change_category() {   
 28var new_category_index = document.all.categoryid.selectedIndex;   
 29var new_subcategory_index = 0;   
 30var new_grand_subcategory_index = 0;   
 31document.all.subcategoryid.options.length = 0;   
 32for (i = 0; i < subcategory_array[new_category_index].length; i ++) {   
 33var this_option = new Option;   
 34this_option.text = subcategory_array[new_category_index][i];   
 35this_option.value = subcategory_id_array[new_category_index][i];   
 36document.all.subcategoryid.options[i] = this_option;   
 37}   
 38document.all.subcategoryid.selectedIndex = new_subcategory_index;   
 39document.all.grandcategoryid.options.length = 0;   
 40for (i = 0; i < grand_subcategory_array[new_category_index][new_subcategory_index].length; i ++) {   
 41var this_option = new Option;   
 42this_option.text = grand_subcategory_array[new_category_index][new_subcategory_index][i];   
 43this_option.value = grand_subcategory_id_array[new_category_index][new_subcategory_index][i];   
 44document.all.grandcategoryid.options[i] = this_option;   
 45}   
 46document.all.grandcategoryid.selectedIndex = new_grand_subcategory_index;   
 47}   
 48function change_subcategory_category() {   
 49var new_category_index = document.all.categoryid.selectedIndex;   
 50var new_subcategory_index = document.all.subcategoryid.selectedIndex;   
 51var new_grand_subcategory_index = 0;   
 52document.all.grandcategoryid.options.length = 0;   
 53for (i = 0; i < grand_subcategory_array[new_category_index][new_subcategory_index].length; i ++) {   
 54var this_option = new Option;   
 55this_option.text = grand_subcategory_array[new_category_index][new_subcategory_index][i];   
 56this_option.value = grand_subcategory_id_array[new_category_index][new_subcategory_index][i];   
 57document.all.grandcategoryid.options[i] = this_option;   
 58}   
 59document.all.grandcategoryid.selectedIndex = new_grand_subcategory_index;   
 60}   
 61</script>
 62<form action="t_list.asp" method="POST" name="form1">
 63<center>   
 64选择专业：<select id="categoryid" onchange="change_category();" size="1" style="COLOR: #0066ff">
 65<option selected="" value="0">全部</option>
 66<option>1</option>
 67</select>   
 68选择班级：<select id="subcategoryid" onchange="change_subcategory_category();" size="1" style="COLOR: #0066ff">
 69<option selected="" value="0">全部</option>
 70</select>
 71<select id="grandcategoryid"></select>
 72</center>
 73<br/>
 74<script language="javascript">   
 75  
 76var i;   
 77  
 78var first_category_index = 0;   
 79  
 80var first_subcategory_index = 0;   
 81  
 82var first_grand_subcategory_index = 0;   
 83  
 84  
 85  
 86for (i = 0; i < category_array.length; i ++) {   
 87  
 88var this_option = new Option;   
 89  
 90this_option.text = category_array[i];   
 91  
 92this_option.value = category_id_array[i];   
 93  
 94document.all.categoryid.options[i] = this_option;   
 95  
 96document.all.categoryid.selectedIndex = first_category_index;   
 97  
 98}   
 99  
100  
101  
102document.all.subcategoryid.options.length = 0;   
103  
104for (i = 0; i < subcategory_array[first_category_index].length; i ++) {   
105  
106var this_option = new Option;   
107  
108this_option.text = subcategory_array[first_category_index][i];   
109  
110this_option.value = subcategory_id_array[first_category_index][i];   
111  
112document.all.subcategoryid.options[i] = this_option;   
113  
114}   
115  
116document.all.subcategoryid.selectedIndex = first_subcategory_index;   
117  
118  
119  
120document.all.grandcategoryid.options.length = 0;   
121  
122for (i = 0; i < grand_subcategory_array[first_category_index][first_subcategory_index].length; i ++) {   
123  
124var this_option = new Option;   
125  
126this_option.text = grand_subcategory_array[first_category_index][first_subcategory_index][i];   
127  
128this_option.value = grand_subcategory_id_array[first_category_index][first_subcategory_index][i];   
129  
130document.all.grandcategoryid.options[i] = this_option;   
131  
132}   
133  
134document.all.grandcategoryid.selectedIndex = first_grand_subcategory_index;   
135  
136</script>
137</form></body>
138</html>