Any browser worth its salt these days has a porn mode, and with version 3.5, Firefox now has one as well. It's called Private Browsing (Internet Explorer's is called InPrivate Browsing), and it works as advertised. When you browse the Web using it, nothing about the session is stored -- no history, no cookies, no temp files, no forms information, no search information, nothing that can show where you've browsed or what you've done. To turn the Las Vegas tag line on its ear: What happens in Firefox doesn't stay in Firefox.

To use Private Browsing, Select Tools --> Start Private Browsing, or else press Ctrl-Shift-P. Unlike with Internet Explorer, a new instance of the browser doesn't launch. Instead, a warning appears, asking you if you want to start a Private Browsing session and telling you that Firefox will save your tabs if you want to start one.

Firefox then closes your existing tabs, and immediately launches a private browsing window. From here, browse the Web as you normally would, and nothing of the session will remain. To end the Private Browsing session, close Firefox as you would normally, or else select Tools --> Stop Private Browsing, or else press Ctrl-Shift-P. The current session ends, and Firefox launches with all of your previous tabs intact.

There are other nice touches for those who don't want other people to know what sites they've been visiting. You can remove all the traces of a site you've visited while you were in a normal browsing session.

This eliminates it not just from the History list, but also kills all traces of the browser on your computer, including cookies and temp files, search history, forms you've filled out, and more.