Ajax控件ModalPopupExtender没有屏蔽弹出窗口以外的内容

Question

下面就是我的页面代码, 点击MORE后,弹出窗口,但是,页面上的其它元素(此页面代码未列出)照样可以点击,输入等.没有被屏蔽起来!  请问是怎么回事? 
<asp:Button runat="server" ID="btnViewMore" Text="More" />
        <asp:Panel ID="pnlViewCustomer" runat="server" CssClass="modalPopup" style="display:none;"> 
            <div style="margin:10px">
                <h1>The service is not available in <span id="Country"></span>.</h1>
                <asp:Button runat="server" ID="viewBox_OK" Text="OK" />
            </div>
        </asp:Panel> 
        <asp:ModalPopupExtender ID="ModalPopupExtender2" runat="server" 
            TargetControlID="btnViewMore" Drag ="true"
            PopupDragHandleControlID="pnlViewCustomer" 
            PopupControlID="pnlViewCustomer"
            BackgroundCssClass="modalBackground"
            DropShadow="false"
            OkControlID="viewBox_OK">
        </asp:ModalPopupExtender>

Answer 1

ModalPopupExtender设置BackgroundCssClass试一下

Answer 2

.modalBackground {
background-color:Gray;
filter:alpha(opacity=70);
opacity:0.7;
}

Answer 3

在弹出层后面加个遮盖层。
ModalPopupExtender设置BackgroundCssClass.lBackground {
    background-color:Gray;
    filter:alpha(opacity=70);
    opacity:0.7;
}

Answer 4

谢谢各位,小弟在网上摘例子学,给出的代码都没有CSS代码! 哈... CSS认识弟,弟不认识CSS呀!谢谢各位~