在写时一定要加上：form 标签外加上<s:head theme=""/>? 才可以；

eg:

<s:head theme=""/>

<s:form name="messageForm" method="post" theme="simple"
	id="messageForm">
	<div class="title">
		数据比对差异报告
	</div>
	<div class="search" id="search">

 	<table class="table">
        <tr>
       <td width="4%" rowspan="3"><img src="${path}/page/wrm/image/search.gif" width="40" height="39"></td>
       <td nowrap="nowrap">消息大类</td>
	        
	   <td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
         
       <td nowrap="nowrap">消息中类</td>
	        
	   <td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
         
         
         <td nowrap="nowrap">消息小类</td>
	        
	   <td><s:select name="message.type" list="msgList" listKey="number" listValue="name" headerKey="" headerValue="--全部--" emptyOption="false" theme="simple" cssClass="select"/></td>
          
		
		 
		 
		<td rowspan="3" align="center">
 	    	<input type='button' onclick="doQuery();"  class="button" value="查 询" /> 
 	    </td>
    </tr>
    <tr>
    
    	<td nowrap="nowrap">标题</td>
         
		
		<td nowrap="nowrap">
		<s:textfield name="message.title" cssClass="text" onchange="getTrimString(this)" />
         </td>
         
         <td nowrap="nowrap">所属区域</td>
         
		
		<td nowrap="nowrap">
		<s:textfield name="message.region" cssClass="text" onchange="getTrimString(this)" />
         </td>
    	
		 
		<td nowrap="nowrap">状态</td>
        <td>
	        <select name="message.dealFlag" id="message.dealFlag" class="select">
			    <option value="">--全部--</option>
			    <option value="1">已处理</option>
			    <option value="0">未处理</option>
			 
			 
			</select>
        
        </td>
        
     
    	
    	
    </tr>
    
    <tr>
    
    
     <td nowrap="nowrap">开始日期</td>
     <td><s:datetimepicker name="startTime" theme="simple" displayFormat="yyyy-MM-dd" /></td>
	        
	        
  	<td nowrap="nowrap">结束日期</td>
    <td><s:datetimepicker name="endTime"  theme="simple" displayFormat="yyyy-MM-dd" /></td>	
     
     <td>
     </td>
     <td>
     </td>
    	
    
    </tr>

    </table>
    </div>.............................<form>

?