Basically, do not intentionally abuse neither frames nor CSS (or server to that matter) and you're on the safe side.
Don't hide. If a SE is not capable or does not want to follow something, well there you can sometimes improve the perception of your page, but hiding beyond agreed rules will put you at risk.
If a bot wants to see something normally allowed to it, let it see.
If a user comes, show him/her the page as there is no search engine.
E.g. even a CSS hiding could be dangerous:
Communication in other languages