The page has one or more <asp:Content> controls that do not correspond with <asp:ContentPlaceHolder> controls in the Master Page.
Correct the problem in Code View:
HeadContent
When I switch AJAXTest.aspx to design view I get the above error. Any ideas?
***************************************************** Site.Master **************************************************
<html lang="en">
<head runat="server">
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title><%: Page.Title %> - My ASP.NET Application</title>
<asp:PlaceHolder runat="server">
<%: Scripts.Render("~/bundles/modernizr") %>
</asp:PlaceHolder>
<webopt:bundlereference runat="server" path="~/Content/css" />
<link href="~/favicon.ico" rel="shortcut icon" type="image/x-icon" />
</head>
<body>
<form runat="server">
<asp:ScriptManager runat="server">
<Scripts>
<%--To learn more about bundling scripts in ScriptManager see http://go.microsoft.com/fwlink/?LinkID=301884 --%>
<%--Framework Scripts--%>
<asp:ScriptReference Name="MsAjaxBundle" />
<asp:ScriptReference Name="jquery" />
<asp:ScriptReference Name="bootstrap" />
<asp:ScriptReference Name="respond" />
<asp:ScriptReference Name="WebForms.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebForms.js" />
<asp:ScriptReference Name="WebUIValidation.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebUIValidation.js" />
<asp:ScriptReference Name="MenuStandards.js" Assembly="System.Web" Path="~/Scripts/WebForms/MenuStandards.js" />
<asp:ScriptReference Name="GridView.js" Assembly="System.Web" Path="~/Scripts/WebForms/GridView.js" />
<asp:ScriptReference Name="DetailsView.js" Assembly="System.Web" Path="~/Scripts/WebForms/DetailsView.js" />
<asp:ScriptReference Name="TreeView.js" Assembly="System.Web" Path="~/Scripts/WebForms/TreeView.js" />
<asp:ScriptReference Name="WebParts.js" Assembly="System.Web" Path="~/Scripts/WebForms/WebParts.js" />
<asp:ScriptReference Name="Focus.js" Assembly="System.Web" Path="~/Scripts/WebForms/Focus.js" />
<asp:ScriptReference Name="WebFormsBundle" />
<%--Site Scripts--%>
</Scripts>
</asp:ScriptManager>
<div class="navbar navbar-inverse navbar-fixed-top">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" runat="server" href="~/">Application name</a>
</div>
<div class="navbar-collapse collapse">
<ul class="nav navbar-nav">
<li><a runat="server" href="~/">Home</a></li>
<li><a runat="server" href="~/About">About</a></li>
<li><a runat="server" href="~/Contact">Contact</a></li>
</ul>
<asp:LoginView runat="server" ViewStateMode="Disabled">
<AnonymousTemplate>
<ul class="nav navbar-nav navbar-right">
<li><a runat="server" href="~/Account/Register">Register</a></li>
<li><a runat="server" href="~/Account/Login">Log in</a></li>
</ul>
</AnonymousTemplate>
<LoggedInTemplate>
<ul class="nav navbar-nav navbar-right">
<li><a runat="server" href="~/Account/Manage" title="Manage your account">Hello, <%: Context.User.Identity.GetUserName() %> !</a></li>
<li>
<asp:LoginStatus runat="server" LogoutAction="Redirect" LogoutText="Log off" LogoutPageUrl="~/" OnLoggingOut="Unnamed_LoggingOut" />
</li>
</ul>
</LoggedInTemplate>
</asp:LoginView>
</div>
</div>
</div>
<div class="container body-content">
****************
<asp:ContentPlaceHolder ID="HeadContent" runat="server">
</asp:ContentPlaceHolder>
************************
<asp:ContentPlaceHolder ID="MainContent" runat="server">
</asp:ContentPlaceHolder>
<hr />
<footer>
<p>© <%: DateTime.Now.Year %> - My ASP.NET Application</p>
</footer>
</div>
</form>
</body>
</html>
***************************************************** AJAXTest.aspx ***************************************
<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="AJAXTest.aspx.cs" Inherits="AJAXTest.AJAXTest" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>
<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:Button ID="Button1" runat="server" Text="Open Popup" />
<asp:Panel ID="Panel1" runat="server">
Welcome to aspnetdotmasters
<asp:Button ID="OK" runat="server" Text="OK" />
</asp:Panel>
<ajaxToolkit:ModalPopupExtender ID="ModalPopupExtender1" runat="server"></ajaxToolkit:ModalPopupExtender>
</asp:Content>