Enable Private Browsing Mode in Firefox 3.5
Firefox 3.5 has lots of new features and one such feature is Private Browsing. If your computer is used by your friends or family members and you would prefer for them not to be able to see what websites you have visited or what files you have downloaded. In such cases, Private Browsing mode is very useful for us. Private Browsing mode allows you to browse the Internet without retaining any of data about which sites and pages you have visited.
How to Enable Private Browsing mode?
In a Private Browsing mode, Firefox would not keep any browser history, search history, download history, web form history, cookies, or temporary internet files. However, files you downloaded and bookmarks you make will be kept.