Can be that, being a curious person, you want to browse the profile of your boss, for example, to find out what are its habits, etc.. discover what could be embarrassing for your Facebook friends. The administration of Facebook has no problem in tracking those who visit the profiles of different users, such as notes or photos. The other users can know if you have visited their profile when they enter any comments or links on their message boards, or if you become fans of their own pages.
If you do not want someone who is not part of your Facebook friends see your profile, you must click your account Privacy, and select Friends Only so that only your friends can see your profile, or you can block some parts of your profile so that everyone can see it. Always pay close attention, because many might gain in having personal information about you.