AJAX 中，让 UpdateProgress 中的内容显示在页面正中央

<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
        <ProgressTemplate>
           
            <div style="position:absolute;left:50%;top:50%;">
               <table width="214" align="center">
               <tr>
               <td>正在加载数据,请稍候</td>
                <td><img src="images/loading_16x16.gif" alt="请稍候"/></td>
               </tr>
               <tr>
               <td colspan="2"><img src="images/pleasewait.gif" /></td>     
               </tr>
               </table>
            </div>
            

        </ProgressTemplate>
    </asp:UpdateProgress>

关键是这句话：

<div style="position:absolute;left:50%;top:50%;">