Modal Popup extender control

Hello ,
i am working with modalpopup extender control. It's not working with the following code.
<asp:ScriptManager ID="ScriptManager" runat="server"></asp:ScriptManager> <asp:UpdatePanel ID="UpdatePanel" runat="server"> <ContentTemplate> <div> <asp:Button ID="btnShow" runat="server" Text="Add" /> <asp:Button ID="btnSearch" runat="server" Text="Search" /> <cc1:ModalPopupExtender ID="mp1" runat="server" PopupControlID="Panel1" TargetControlID="btnShow" CancelControlID="btnClose" BackgroundCssClass="modalBackground" /> <cc1:ModalPopupExtender ID="mp2" runat="server" PopupControlID="Panel2" TargetCon ...