There is no built-in way to remove or disable the feature. You can hide the menu options but the keyboard shortcut to start private browsing will still work. For details see this thread - [https://support.mozilla.com/tiki-view_forum_thread.php?comments_offset=0&comments_threadId=0&comments_parentId=576657&comments_threshold=0&thread_sort_mode=commentDate_asc&forumId=1&time_control=3600#threadId576657 How do i block the private browsing option from my children?] Even with the menu options hidden it is still possible to delete browsing history. If you want to keep track of all sites visited you will need an external option. If this is to keep track of children using the internet, one option is the [http://www1.k9webprotection.com/ K9 Web Protection - Free Internet Filter and Parental Control Software].