HTML呈现出形式

Question

我有这段代码：

<div id="jDialogWarning" class="jDialog">
    <h1 class="DialogTitle">
        Warning!</h1>
    <br />
    <div class="jDialog_form">
        <span id="errWarningMsg"></span>
    </div>
    <div id="UpdateBtn">
        <div class="WideButton" style="float: right; display: block;">
            <a href="#" id="A1" onclick="ContinueToPayment('')">
                <%=SessionManager.AgentDetails!=null ? "Continue" : "Update Reservation" %></a>
        </div>
    </div>
    <div id="AgentFormData" style="display: none">
        <div>
            <span id="AgentVoucherNumber">Agent Voucher Number: </span>
            <asp:TextBox ID="txtAgentVoucherNumber" runat="server" ValidationGroup="AgentValidation"
                MaxLength="10" onkeydown="return DigitsOnly(this)"></asp:TextBox>
            <asp:RegularExpressionValidator ID="RegExVoucherNumber" runat="server" Display="Dynamic"
                ControlToValidate="txtAgentVoucherNumber" ValidationExpression="\d{1,10}" ValidationGroup="AgentValidation"
                ErrorMessage="<%#AwardSystem.Web.Code.ErrorsGetter.GetErrorDescriptionByErrorNumber(AwardSystem.Entities.Enums.eErrorsCodes.InvaludVoucherAgentNumber)%>"></asp:RegularExpressionValidator>
            <asp:RequiredFieldValidator ID="RequiredVoucherNumber" runat="server" ErrorMessage="*"
                Display="Dynamic" Text="Required" ControlToValidate="txtAgentVoucherNumber" ValidationGroup="AgentValidation"></asp:RequiredFieldValidator>
        </div>
        <div>
            <span id="AgentEmailAddress">Agent Email Address: </span>
            <asp:TextBox ID="txtAgentEmailAddress" runat="server" ValidationGroup="AgentValidation"></asp:TextBox>
            <asp:RegularExpressionValidator ID="RegExEmail" runat="server" ControlToValidate="txtAgentEmailAddress"
                ValidationExpression="^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$" ValidationGroup="AgentValidation"
                ErrorMessage="<%#AwardSystem.Web.Code.ErrorsGetter.GetErrorDescriptionByErrorNumber(AwardSystem.Entities.Enums.eErrorsCodes.invalidEmailAddress)%>"></asp:RegularExpressionValidator>
            <asp:RequiredFieldValidator Text="Required" ID="RequiredEmail" runat="server" ControlToValidate="txtAgentEmailAddress"
                ErrorMessage="*" Display="Dynamic" ValidationGroup="AgentValidation"></asp:RequiredFieldValidator>
        </div>
        <div class="WideButton">
            <asp:LinkButton ID="btnContinue" runat="server" Text="Continue to ticketing" OnClick="UpdateReservation"
                ValidationGroup="AgentValidation" CausesValidation="true" />
        </div>
    </div>
    <div class="NarrowButton" style="float: right; margin-right: 10px">
        <a href="#" id="CloseBtn">Close</a>
    </div>
    <a class="close_x close sprited" href="#" id="Close"></a>
</div>

它位于：

<asp:Content ID="Content4" ContentPlaceHolderID="MainContentPlaceHolder" runat="server"></asp:Content>

页面本身使用定义表单的母版页。此内容在表单内。然而，渲染的html在表单之外排除了这个div。知道为什么吗？