ajax的loading显示在gridview的位置

< body >
     < form id = " form1 "  runat = " server " >
     < asp:ScriptManager ID = " ScriptManager1 "  runat = " server " >
     </ asp:ScriptManager >
     < asp:UpdatePanel ID = " UpdatePanel1 "  runat = " server " >
         < ContentTemplate >
             < div style = " background-color:Beige; " >
                 < asp:GridView ID = " GridView1 "  runat = " server "  AutoGenerateColumns = " False "  
                    DataSourceID = " AccessDataSource1 " >
                     < Columns >
                         < asp:BoundField DataField = " 图书简介 "  HeaderText = " 图书简介 "  SortExpression = " 图书简介 "   />
                         < asp:BoundField DataField = " 图书名称 "  HeaderText = " 图书名称 "  SortExpression = " 图书名称 "   />
                         < asp:BoundField DataField = " 作者 "  HeaderText = " 作者 "  SortExpression = " 作者 "   />
                     </ Columns >
                 </ asp:GridView >
                 < div style = " position:absolute; top:100px; left:300px; font-size:40px; color:Red; " >
                     < asp:UpdateProgress ID = " UpdateProgress1 "  runat = " server " >
                         < ProgressTemplate >
                             < div > 更新数据，请稍候…… </ div >
                         </ ProgressTemplate >
                     </ asp:UpdateProgress >
                 </ div >
                
             </ div >
             < asp:Button ID = " Button1 "  runat = " server "  Text = " Button "  onclick = " Button1_Click "   />
         </ ContentTemplate >
     </ asp:UpdatePanel >
     < asp:AccessDataSource ID = " AccessDataSource1 "  runat = " server "   DataFile = " ~/App_Data/电子交易.mdb "  
         SelectCommand = " SELECT [图书简介], [图书名称], [作者] FROM [书籍信息] " >
     </ asp:AccessDataSource >
     </ form >
     </ body >

页面上用到了 UpdateProgress，以便在进行各种操作时显示一个等待图标，给用户解解闷，好让他们在漫长的等待结果的岁月中不那么烦躁，知道系统正在忙。

形如：

< asp:UpdateProgress ID = " UpdateProgress1 "  runat = " server "   >

     < ProgressTemplate >

     < img src = " ../images/loading.gif "  alt = " 请稍候 "   />

</ ProgressTemplate >

</ asp:UpdateProgress >

可是这样写的话图标就歪在一边，不显眼。如果写上个绝对定位，比如

style = " position:absolute;left:400px;top:300px; " ,可这仅仅适合800 * 600的屏幕，而用户的屏幕分辨率千差万别。

最后发觉可以用百分比，这样写：

< asp:UpdateProgress ID = " UpdateProgress1 "  runat = " server "   >

     < ProgressTemplate >

     < img src = " ../images/loading.gif "  alt = " 请稍候 "  style = " position:absolute;left:50%;top:50%; " />

</ ProgressTemplate >

</ asp:UpdateProgress >