Hi
Balongi,
Please use this code it is working fine.
This is modal popup button code (where you can open the popup)
<asp:HyperLink runat="server" ID="hylSelectInstruction" NavigateUrl="javascript:void(0)"
Text="Select Standard Instruction"></asp:HyperLink>
This is modal popup code
<asp:ModalPopupExtender ID="ModalPopupExtender1" BehaviorID="bInstruction" runat="server"
TargetControlID="hylSelectInstruction" PopupControlID="pnlInstruction" BackgroundCssClass="popupwrapper_transparentbg"
DropShadow="false" PopupDragHandleControlID="pnlInstructionDragHandle" OkControlID="lbtnInstructionCancel"
RepositionMode="RepositionOnWindowScroll" />
<asp:Panel runat="server" ID="Panel1" Style="display: none; width: 600px;
height: 300px;">
<table width="100%" cellpadding="0" cellspacing="0" border="0">
<tr>
<td >
<%--Yor modal popup form controls comes here.. --%>
</td>
</tr>
</table>
</asp:Panel>
Thanks,
Imdadhusen