<%@ Page Language="C#" MasterPageFile="~/MyMasterPageNested.master"  %>
<asp:content id="MyContent" contentplaceholderid="MyContentPH2" 
             runat="server" > 
   <asp:label id="lbl"          Height="100%"     Width="100%"
              BackColor="Black" ForeColor="White" runat="server" 
              Font-Size="XX-Large">Content of Default.aspx</asp:label>  
</asp:content>