That way no one can install weird apps - even if there aren't really any porn apps per se on Mac, it's just the best practice. For anyone else, it's their restricted account or guest access. also, for any user: It's YOUR computer, so only you should have access to the Administrator user. this site has a long list of sites you probably would want to add to your hosts file. To add addresses to blocked sites list in hosts file, see So allow the users to only access Safari as a browser So if you have other browsers installed, and allow the users to access those browsers, they can browse whatever they want. Note: the built-in controls are for Safari. Your children/other users with restricted access use a restricted account, and can't bypass the limitations e.g. Make a list of pre approved sites, and all the new sites will have to be approved by you, who use the administrator account.
For (mostly) children: use the parental controls that come with Mac OS X (search in System Preferences). For any user you want to control (I would guess it's for other users on your Macs?), you could e.g.
