I would like to deactivate Compiz for a single window. Is this possible?
No, Compiz is a Window Manager so it's all or nothing. If it's non graphical you could switch to Ctrl+Alt+F2
From previous Q&A How can I use a .html file as desktop background/wallpaper?
I'd like to add a neat trick to Sabacon's answer about using Prism...
You can turn Prism into a sort of widget by removing the windowframe. Add this line in Compiz - Extras/Windows Decorations on the Decorations Windows line add this to the end
This is what I use to remove the windowframe on all maximized windows and all prism windows