Private browsing is getting added to firefox 3.1. Google chrome introduced it and Microsoft’s Internet explorer is working on it as well.
Private browsing is all about browsing the web without leaving any traces of data on your PC/computer. Most web browsers record a lot of user’s data, under the pretext of using it to improve browsing experience.However, private browsing will pause collection of the users’ data. Note that it neither lets you be anonymous from websites or your ISP nor does it it help to protect your computer from spywares.
When you switch on private browsing, you are just saying firefox, not to store any data (on your computer), that can be used to tell the pages you have visited. Private browsing is useful on shared computers.
Check out the announcement on private browsing.According to that blog, you will have to uncheck the private browsing submenu under Tools, to close your private session. The unchecking action discards all the data from your private session, and restores your non-private browsing session, just like it was before entering the Private Browsing mode.
But I believe that the the data will be discarded, even if firefox is closed without unchecking private browsing.
So if you work on shared computers, but still have a lot of concerns about privacy, then you can make use of private browsing in firefox.
If you are interested in making Firefox always start in Private Browsing mode, go to the about:config page, type browser.privatebrowsing.autostart in the filter text box and double click the entry to make its value true.Restart firefox and you will be in private browsing mode.