With the launch of Firefox v42 (and up) they introduced an adBlocker in the browser. The ad blocking feature is available (by default) during the use of Private Browsing.

But if you don't want to see those advertisements, and for some reason you don't want to use Private Browsing (like me), than you're out of luck (by default). There's no normal way to enable this feature without the use of Private Browsing (or use an adBlocker add-on for Firefox). Thankfully, Firefox uses a config module in which you can tweak almost everything.... including the Tracking Protection.