Adding Frames in ASP.NET

Hi,
I am trying to add a frame within the "MainContent" of the webpage so that it can load 2 external websites (msnbc.com and google.com in my example) in that area, but I cannot seem to get them to load.  I cannot even see the "Frames" title that I put in the html code.  I am using the default Site Master page that came with Visual Web Developer 2010 Express Beta.  The code that I am trying to run is below.  Am I missing something in my code?  Is there another way to open an external website within the "MainContent" area? 
Thanks

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</ ...