Master Page

Hi All,
I have create one master page and now i am trying to put this in may main page. Here are the codes but i am getting this error
Only Content controls are allowed directly in a content page that contains Content controls.
Please help
Master Page
 <form id="form1" runat="server">
   
        <div>
            <asp:ContentPlaceHolder ID="Header" runat="server">
                <asp:Label ID="Label1" runat="server" Text="Header..." Font-Bold="True" Font-Italic="False"
                    Font-Names="Verdana" Font- ...