And, on an unrelated note.
When a visitor is on your checkout page the only thing you want them to do is checkout.
So disable the sidebar, menu, etc. on that page.
Have a custom footer that only has links to whatever legal disclaimers are required for you (I'm not qualified to give you advice in that area--talk to your attorney).
Basically the only option is to checkout or leave. All the other stuff is distracting.
When someone is about to pay you, you don't want that person to click on a "Recent News" link instead.
There are probably plugins to disable menus on certain pages, but I use a custom checkout page template.