Ajax控件问题


 <style type="test/css">
       .modalBackground {
        background-color: Gray;
        filter: alpha(opacity=50);
        opacity: 0.5;
       }  </style><asp:Panel ID="gotoLogin" runat="server" style=" display:none">
            <table style=" background-color:#FBDC7F" border="1" rules="rows">
                <tr>
                    <td align="center" colspan="2">
                        <font size="+2" style=" font-weight:bold" color="#AFAA13">登录后才能够回帖！！！</font>
                    </td>
                </tr>
                <tr>
                    <td align="right">用户名：</td>
                    <td align="left">
                        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td align="right">密&nbsp;&nbsp;码：</td>
                    <td align="left">
                        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td colspan="2" align="center">
                        <asp:Button ID="Button3" runat="server" Text="登   录" onclick="Button3_Click" />&nbsp;&nbsp;
                        <asp:Button ID="Button4" runat="server" Text="取   消" />
                    </td>
                </tr>
                <tr>
                    <td colspan="2">&nbsp;</td>
                </tr>
            </table>
        </asp:Panel>
        
        <input id="hid" type="hidden" runat="server" />
        
        <asp:ModalPopupExtender ID="ModalPopupExtender1" runat="server"
             TargetControlID="hid"
             PopupControlID="gotoLogin"
             CancelControlID="Button4"
             Drag="true"
             DropShadow="true"
             PopupDragHandleControlID="gotoLogin"
             BackgroundCssClass="modalBackground">
        </asp:ModalPopupExtender>
    现在问题就是：如果我没有登录就点击“发帖”按钮的时候Panel是会弹出来，但是并没有达到蒙版的效果，就是除了panel外其它部分变成暗灰色。好像是没有调用样式。请高手指点。