First you add Ajax toolkit dll in your Application. After that use the
<asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="Gdvwratebtn"
BackgroundCssClass="modalBackground" PopupControlID="ratepopup" DropShadow="true">
</asp:ModalPopupExtender>
and
create the asp button & panels
inside of panel use asp all controls as your wish
**TargetControlID="Gdvwratebtn" is the Button ID
**PopupControlID="ratepopup" is the Panel ID