OK when you go onto your computer click the icon (windows xp) Start button or round logo Vista Windows 7
then click near shut down 'Switch User' then you can create a login account with a password.
Once you logged in you can download and use any browser that you want and websites or cookies used on the web browser will only apply to the user name and account!
Example: User Sandy logs in and visits a Marmite fetish website and logs in and sends pms back an fourth when sandy has finshed using the computer she logs off!
Then a new user logs in Tim he has no knowledge of Marmite websites and will not show up in history.
If any of you ask any website to remember me when loging into any website and you either bookmark this site (favorites)
then anyone going through the fav list will be able to read you pms and profiles etc same with hotmail.
Keyboard keys do not have finger print detection yet so the computer treats the default user as anyone who uses it.
Key thing when using a computer if its shared in a house is Create your own passworded user account and log off when you finished.
That way your life will be easier online and you can tell login websites to remember me etc (not keep loging in on every visit)
No idea on Apples sorry (I like flexability)