When I visit my research sites I can just use Private Browsing. Every web browser I know of has some form of it, in Chrome it is Incognito Mode.
Also once I had two friends stay over. After that I sat on the couch and opened up my iPod's web browser. loving 7 TABS OF HENTAI AND ADULT SOCIAL NETWORKS. HOLY forget. The history had things like beastiality sites (those may have been mine, though...) and Hentai games.
One of them admitted to it a month later.