Master pages allow you to create a consistent look and behavior for all the pages (or group of pages) in your web application.
I have a site that is giving me the following error:
Content controls are allowed only in content page that references a master page.
My MasterPage
<%@ Master Language="C#" AutoEventWireup="true" Inherits="mstrPageMain" Codebehind="mstrPageMain.master.cs" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<meta http-equiv="x-ua-compatible" content="IE=10"/>
<title>Untitled Page</title>
</head>
<body>
<script type="text/javascript">
...
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