HoverMenuExtender is how appearing and appearing inside grid

Hi,

I have below code for hovermenu extender

 <ItemTemplate>
               <asp:ImageButton ID="btnEdit" runat="server" ImageUrl="~/Images/boxes.png" CommandArgument='<%#Eval("ShipmentID") %>'
                                             Width="15" Height="15" />
                            <ajax:HoverMenuExtender ID="hmextenderAction" runat="server" TargetControlID="btnEdit" PopupControlID="pnlHover"
                                                     PopDelay="50" OffsetX="40" OffsetY="-5"></ajax:HoverMenuExtender>
                            <!-- pop up hover start -->
                            <asp:Panel ID="pnlHover" runat="server" HorizontalAlign="right" CssClass="popuphover">
                                <div class="hoverpanel">                                    
                                    <asp:LinkButton ID="lnkEdit" CommandName="goDetail" CommandArgument='<%# Eval("ShipmentID") %>' CssClass="contentfont nounderline"
                                                    runat="server" Text="Edit" CausesValidation="false"></asp:LinkButton><br />
                                                                
                                </div>
                            </asp:Panel>

extender is not showing or appearing on move over image. but it is showing always under need of image. please advice,

might need to fix something.

Thanks