I use Windows Vista as an Operating system. I,also using Firefox Version 3.6.20. I want to Block some websites such as www.facebook.com as my younger brother is also sharing the same PC,so I don't want that he will do any malicious activity OR open any website which really redirect him in the wrong way. Is it possible to block websites without using Add-ons? If,possible please provide me the expedient way of getting it.