In addition to what MissB said, we have a couple of minor tricks in our premium area to see some normally hidden things on people's Facebook profiles (like if they may have sent someone some naughty gifts, or drinks, etc.) and if/when new tricks come along, they get posted in there. For the most part though, at the moment, Facebook is pretty locked up tight, but you will need a Facebook account in order to see anything at all, assuming they do have some things out in the open.

Unless you leave a comment or something they will not know you visited their page. Visiting their page however is the issue. You would need to be friends with them unless their profile is public to everyone or people in their networks (networks=city, grad. class, etc. are examples) here is a clickable link for more info. if their profile is private, you could request their friendship... it's not such a longshot you never know! people are adding their parents as friends nowadays!
~karma: i'm countin on it~