I know this issue has been addressed in the past however I have applied the corrections to the site.master and the default aspx pages with no success. Below are my site.master and default.aspx contents. Any and all help is very much appreciated.
<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site.master.cs" Inherits="CAPNAT.SiteMaster" %>
<%@ Register TagPrefix="ajax" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<!DOCTYPE html>
<html lang="en">
<head runat="server">
<meta charset="utf-8" />
<title><%: Page.Title %> - Custom APN Configuration Tool</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" />
<meta name="viewport" content="width=device-width" />
<asp:ContentPlaceHolder runat="server" ID="HeadContent" />
</head>
<body>
<form runat="server">
<ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
<Scripts>
<%--Framework Scripts--%>
<asp:ScriptReference Name="jquery" />
<asp:ScriptReference Name="jquery.ui.combined" />
<asp:ScriptReference Name="WebForms.js" Path="~/Scripts/WebForms/WebForms.js" />
<asp:ScriptReference Name="WebUIValidation.js" Path="~/Scripts/WebForms/WebUIValidation.js" />
<asp:ScriptReference Name="MenuStandards.js" Path="~/Scripts/WebForms/MenuStandards.js" />
<asp:ScriptReference Name="GridView.js" Path="~/Scripts/WebForms/GridView.js" />
<asp:ScriptReference Name="DetailsView.js" Path="~/Scripts/WebForms/DetailsView.js" />
<asp:ScriptReference Name="TreeView.js" Path="~/Scripts/WebForms/TreeView.js" />
<asp:ScriptReference Name="WebParts.js" Path="~/Scripts/WebForms/WebParts.js" />
<asp:ScriptReference Name="Focus.js" Path="~/Scripts/WebForms/Focus.js" />
<asp:ScriptReference Name="WebFormsBundle" />
<%--Site Scripts--%>
</Scripts>
</ajaxToolkit:ToolkitScriptManager>
Default.aspx
<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/MasterPages/Site.Master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="CAPNAT._Default" %>
<%@ Register TagPrefix="ajax" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<asp:Content runat="server" ID="FeaturedContent" ContentPlaceHolderID="FeaturedContent">
<section class="featured">
<div class="content-wrapper">
<hgroup class="title">
<h1><%: Title %>.</h1>
<h2>Modify this template to jump-start your ASP.NET application.</h2>
</hgroup>
Comments: It seems that this error is caused by ToolkitScriptManager. Starting with the v15.1 release, we have removed it. So now, this problem is resolved.
<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site.master.cs" Inherits="CAPNAT.SiteMaster" %>
<%@ Register TagPrefix="ajax" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<!DOCTYPE html>
<html lang="en">
<head runat="server">
<meta charset="utf-8" />
<title><%: Page.Title %> - Custom APN Configuration Tool</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" />
<meta name="viewport" content="width=device-width" />
<asp:ContentPlaceHolder runat="server" ID="HeadContent" />
</head>
<body>
<form runat="server">
<ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
<Scripts>
<%--Framework Scripts--%>
<asp:ScriptReference Name="jquery" />
<asp:ScriptReference Name="jquery.ui.combined" />
<asp:ScriptReference Name="WebForms.js" Path="~/Scripts/WebForms/WebForms.js" />
<asp:ScriptReference Name="WebUIValidation.js" Path="~/Scripts/WebForms/WebUIValidation.js" />
<asp:ScriptReference Name="MenuStandards.js" Path="~/Scripts/WebForms/MenuStandards.js" />
<asp:ScriptReference Name="GridView.js" Path="~/Scripts/WebForms/GridView.js" />
<asp:ScriptReference Name="DetailsView.js" Path="~/Scripts/WebForms/DetailsView.js" />
<asp:ScriptReference Name="TreeView.js" Path="~/Scripts/WebForms/TreeView.js" />
<asp:ScriptReference Name="WebParts.js" Path="~/Scripts/WebForms/WebParts.js" />
<asp:ScriptReference Name="Focus.js" Path="~/Scripts/WebForms/Focus.js" />
<asp:ScriptReference Name="WebFormsBundle" />
<%--Site Scripts--%>
</Scripts>
</ajaxToolkit:ToolkitScriptManager>
Default.aspx
<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/MasterPages/Site.Master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="CAPNAT._Default" %>
<%@ Register TagPrefix="ajax" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<asp:Content runat="server" ID="FeaturedContent" ContentPlaceHolderID="FeaturedContent">
<section class="featured">
<div class="content-wrapper">
<hgroup class="title">
<h1><%: Title %>.</h1>
<h2>Modify this template to jump-start your ASP.NET application.</h2>
</hgroup>
Comments: It seems that this error is caused by ToolkitScriptManager. Starting with the v15.1 release, we have removed it. So now, this problem is resolved.