title: ModalPopup not working in the Content Page of the Master Page
body: <p><strong>This is my Content Page</strong> </p>
  
  <pre><code>&lt;%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true"
      CodeFile="Default.aspx.cs" Inherits="_Default" %&gt;
  
  &lt;%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %&gt;
  &lt;asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server"&gt;
      &lt;link type="text/css" rel="Stylesheet" href="StyleSheet.css" /&gt;
  &lt;/asp:Content&gt;
  &lt;asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server"&gt;
      &lt;asp:ScriptManager ID="script1" runat="server"&gt;
      &lt;/asp:ScriptManager&gt;
      &lt;asp:UpdatePanel ID="up1" runat="server" UpdateMode="Conditional"&gt;
          &lt;ContentTemplate&gt;
              &lt;asp:Panel ID="pnl1" runat="server" Height="200" Width="200" CssClass="modalPopup"&gt;
                  &lt;h1&gt;
                      Hello World
                  &lt;/h1&gt;
              &lt;/asp:Panel&gt;
              &lt;asp:Button ID="btnShow" runat="server" Text="Show" /&gt;
              &lt;cc1:ModalPopupExtender ID="mpEditComment" runat="server" PopupControlID="pnl1" TargetControlID="btnShow"
                  BackgroundCssClass="modalBackground"&gt;
              &lt;/cc1:ModalPopupExtender&gt;
          &lt;/ContentTemplate&gt;
      &lt;/asp:UpdatePanel&gt;
  &lt;/asp:Content&gt;
  </code></pre>
  
  <p><strong>This is My Master Page</strong></p>
  
  <pre><code>&lt;%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage" %&gt;
  
  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head runat="server"&gt;
      &lt;title&gt;&lt;/title&gt;
      &lt;asp:ContentPlaceHolder ID="head" runat="server"&gt;
      &lt;/asp:ContentPlaceHolder&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;form id="form1" runat="server"&gt;
      &lt;asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server"&gt;
      &lt;/asp:ContentPlaceHolder&gt;
      &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>