checkbox标签选中不了，不知道为什么，请高手帮帮忙，如果用s:checkbox，要怎么做，我用s：checkbox后页面显示都乱了

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
     <base href="<%=basePath%>">
    
    <title>DormDirty</title>
    
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">    
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
    <link href="css/css.css" rel="stylesheet" type="text/css" />
    <link href="css/style.css" rel="stylesheet" type="text/css" />
    
  </head>
  <script type="javascript/text">
      function selectAll()
{
var obj = document.fom.elements;
for (var i=0;i<obj.length;i++){
if (obj[i].name == "listCheck"){
obj[i].checked = true;
}
}}
function unselectAll(listCheck)
{
var obj = document.fom.elements;
for (var i=0;i<obj.length;i++){
if (obj[i].name == "listCheck"){
obj[i].checked = false;
}
}
}
  </script>
 <body>
<form name="fom" id="fom" method="post" action="">
<table width="100%" border="0" cellspacing="0" cellpadding="0">
  
  <tr>
    <td height="30">      <table width="100%" border="0" cellspacing="0" cellpadding="0">
        <tr>
          <td height="62" background="Images/nav04.gif">
            
   <table width="98%" border="0" align="center" cellpadding="0" cellspacing="0">
    <tr>
  <td width="21"><img src="Images/ico07.gif" width="20" height="18" /></td>
  <td width="538">查看内容：按时间：
<input name="textfield" type="text" size="12" readonly="readonly"/>
<span class="newfont06">至</span>
<input name="textfield" type="text" size="12" readonly="readonly"/>
<input name="Submit4" type="button" class="right-button02" value="查 询" /></td>
   
    </tr>
          </table></td>
        </tr>
    </table></td></tr>
  <tr>
    <td><table id="subtree1" style="DISPLAY: " width="100%" border="0" cellspacing="0" cellpadding="0">
        <tr>
          <td><table width="95%" border="0" align="center" cellpadding="0" cellspacing="0">
            <tr>
              <td height="20"><span class="newfont07">选择：</span><input type="button" value="全选"  onclick="selectAll();"/>-<input type="button" value="反选"  onclick="unselectAll();"/>               <input name="Submit" type="button" class="right-button08" value="删除所选任务" />
              <input name="Submit2" type="button" class="right-button08" value="添加任务" onclick="link();"/></td>
            </tr>
              <tr>
                <td height="40" class="font42">
<table width="100%" border="0" cellpadding="4" cellspacing="1" bgcolor="#464646" class="newfont03">
 <tr class="CTitle" >
                     <td height="22" colspan="9" align="center" style="font-size:16px">宿舍卫生情况列表</td>
                  </tr>
                  <tr bgcolor="#EEEEEE">
    <td width="5%" align="center" height="30">选择</td>
                    <td width="10%">序号</td>
<td width="11%">宿舍编号</td>
                    <td width="6%">得分</td>
<td width="14%">检查时间</td>
<td width="11%"><p> 周数</p></td>
<td width="11%"><p>学期</p></td>
<td width="12%"><p>宿舍ID</p></td>
<td width="17%">操作<s:debug/></td>
                  </tr>
                  <s:iterator value="list">
                  <tr bgcolor="#FFFFFF">
    <td><input type="checkbox" name="listCheck"/></td>
    
                    <td><s:property value="dormId"/></td>
                    <td><s:property value="dormNo"/></td>
                    <td><s:property value="score"/></td>
                    <td><s:property value="checkTime"/></td>
                    <td><s:property value="week"/></td>
                    <td><s:property value="term"/></td>
                    <td><s:property value="dormId"/></td>
                    
                    
                    <td><a href="editrenwu.htm">编辑</a><a href="listrenwumingxi.htm">|</a>
<a href="#">删除</a></td>
                  </tr>
                  </s:iterator>
            </table></td>
        </tr>
      </table>
      <s:url id="url_pre" value="DormDirtyAction.action">
         <s:param name="pageNow" value="pageNow-1"></s:param>
     </s:url>
     <s:url id="url_next" value="DormDirtyAction.action">
         <s:param name="pageNow" value="pageNow+1"></s:param>
     </s:url>      
      <table width="95%" border="0" align="center" cellpadding="0" cellspacing="0">
        <tr>
          <td height="6"><img src="Images/spacer.gif" width="1" height="1" /></td>
        </tr>
        <tr>
          <td height="33"><table width="100%" border="0" align="center" cellpadding="0" cellspacing="0" class="right-font08">
              <tr>
                <td width="50%">共 <span class="right-text09">${session.pageCount}</span> 页 | 第 <span class="right-text09">${pageNow}</span> 页</td>
                <td width="49%" align="right">[<s:a href="DormDirtyAction.action?pageCount=1" class="right-font08">首页</s:a> | <s:a href="%{url_pre}" class="right-font08">上一页</s:a> | <s:a href="%{url_next}" class="right-font08">下一页</s:a> | <a href="DormDirtyAction.action?pageNow=<s:property value='#session.pageCount'/>" class="right-font08">末页</a>] </td>
                <td width="1%"><table width="20" border="0" cellspacing="0" cellpadding="0">
                    
                </table>
      
      
    </td>
        </tr>
      </table></td>
  </tr>
</table>
</form>
</body>
</html>