Here's the master page as well:

<%@ Page Language="C#" MasterPageFile="~/MasterPages/Newsletter.master" Trace="false"   Culture="en-GB" UICulture="en-GB" %>

<%@ Register TagPrefix="projectControls" Namespace="MyProject.Controls" Assembly="MyProject.Controls" %>
<%@ Import Namespace="MyProject.Controls" %>

<asp:content id="content2" contentplaceholderid="_mainContent" runat="server">
    <table width="100%">
        <tr>
            <td>
                <projectControls:ManageContent ID=ManageContent Runat=server />               
            </td>
        </tr>
    </table>
</asp:content>