Psst: the private browsing mode in your current web browser probably isn't that private. It'll (usually) get rid of your history and cookies, but it won't prevent cross-site trackers from getting a feel for what you're doing. However, you now have an easy way to deal with that -- Mozilla has released a finished version of Firefox with its promised stricter Private Browsing mode. Switch it on and you'll get tracking protection that blocks code from those ads and social services that follow you from site to site. There's also a central control panel on the desktop for managing privacy and security, including the option to turn tracking protection off if it's breaking an important page.
There are a few more perks, too, depending on what platform you're running. Desktop users now have a one-click option to mute audio in tabs, much your friends using Chrome. On Android, you can get both direct voice searching from the address bar as well as kid-safe browsing on a tablet's restricted profile. The upgraded Firefox is available now on all platforms, so give it a shot if you're interested in any of the new features -- especially if you don't want the internet looking over your shoulder.