HI
Here is my modalpopup
When I click the button "btnOk" inside my panel, then the popup disappears.
<ajaxToolkit:ModalPopupExtender ID="ModalPopupTextBoxEmpty" runat="server"
TargetControlID="Image6" PopupControlID="PNLTextBoxEmpty" BackgroundCssClass="modalBackground" OkControlID="btnOk"
DropShadow="false" />