web-----------------------------JavaScrip
<script language="javascript">
   function ShowWaitInfo()
   {
    var intFormWidth;
    var intFormHeight;
    var intDivTop;
    var intDivLeft;
   
    intFormWidth = window.screen.availWidth;
    intFormHeight = window.screen.availHeight;
   
    intDivTop = (intFormHeight - 200 - 200) / 2;
    intDivLeft = (intFormWidth - 500) /2;
   
    document.all("divWaitInfo").style.visibility="visible";
    document.all("divWaitInfo").style.left = intDivLeft;
    document.all("divWaitInfo").style.top = intDivTop;
   }
  </script>
------------------------------------------html
<DIV id="divWaitInfo" #009999 thin solid; BORDER-TOP: #009999 thin solid; LEFT: 300px; VISIBILITY: hidden; BORDER-LEFT: #009999 thin solid; WIDTH: 278px; BORDER-BOTTOM: #009999 thin solid; POSITION: absolute; TOP: 130px; HEIGHT: 144px; BACKGROUND-COLOR: white"
       ms_positioning="FlowLayout">
       <TABLE id="tblWaitInfo" height="100%" cellSpacing="1" cellPadding="1" width="100%" border="0">
        <TR>
         <TD></TD>
         <TD></TD>
         <TD></TD>
         <TD></TD>
        </TR>
        <TR>
         <TD 114px"></TD>
         <TD align="right" 114px">正在查询,请稍候...</TD>
         <TD 114px"><FONT face="宋体"><asp:image id="Image1" runat="server" ImageUrl="../../../Images/Clock.gif"></asp:image></FONT></TD>
         <TD 114px"><FONT face="宋体"></FONT></TD>
        </TR>
        <TR>
         <TD></TD>
         <TD></TD>
         <TD><FONT face="宋体"></FONT></TD>
         <TD><FONT face="宋体"></FONT></TD>
        </TR>
       </TABLE>
      </DIV>
------------------------------------------C#
    btnQuery.Attributes["onclick"] = "ShowWaitInfo();";