以下一段代码中编译器不识别<headertemplate>，<itemtemplate>，<footertemplate>
为啥？ 请高手指教。谢谢！


<controls:simplepager id="items" runat="server" pagesize="4" emptytext="记录为空" onpageindexchanged="PageChanged">
                    <headertemplate>
                        <table cellpadding="0" cellspacing="0">
                            <tr class="gridHead">
                                <td>编号</td>
                                <td>名称</td>
                                <td>价格</td>
                                <td>&nbsp;</td>
                            </tr>
     </headertemplate>
     <itemtemplate>
    <tr class="gridItem">                    <td><%# DataBinder.Eval(Container.DataItem, "Id") %></td>        <td><a href='ItemDetails.aspx?itemId=<%# DataBinder.Eval(Container.DataItem, "Id") %>' class="text"><%# DataBinder.Eval(Container.DataItem, "Name") %></a></td>
                            <td class="num"><%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %></td>
                            <td><a href='ShoppingCart.aspx?itemId=<%# DataBinder.Eval(Container.DataItem, "Id") %>'><img src="Images/buttonAdd.gif" alt="Add to Cart" border="0"></a></td>
                        </tr>
   </itemtemplate>
   <footertemplate>
</table>
</footertemplate>
</controls:simplepager>