Hi Cliff,
Since this question does not relate to the book directly, you're better off posting in a general ASP.NET category from this list:
http://p2p.wrox.com/asp-net-4-5-709/ This way you'll attract move viewers and others can join and learn from the discussion too.
That said, the control probably renders a CSS block element (like a table or a div) which means content following it will be moved to the next line. To place your content side by side, you can use the same mechanism as used for the Admin menu and the Sidebar: use the CSS float property to float the new content to the right of the DetailsView.
Hope this helps,
Imar