If you are using broadband, then I would reccomend using a router or firewall that will log all internet activity. Some routers and firewall can even email you a list of all websites visited at scheduled time frames. If you do not want someone visiting certain sites, then a hardware firewall or router is the way to go as you can restrict websites. I do not think you can stop anyone from visiting any given website as this is imposible! but you can keep track of a users web browsing history with the above mentioned devices.