Firefox 42 was just released with major improvements for both Android and desktop. Firefox now has tracking blocking built in! By default it is only on during private browsing, to enable it for general use go to about:config and scroll down to privacy.trackingprotection.enabled and set the value to true. This works on both mobile and desktop. It will block many ads and most trackers and works similarly to Ghostery or Privacy Badger.
For desktop use, Firefox also now includes an icon to show which tab is playing audio and the ability to mute it without leaving the current tab. This is a catch up feature that has been available in Chrome for some time. Still a welcome addition.
Firefox usage is in decline and that is a shame. The one browser coded by a non-profit with keeping the web open as its stated goal. Safari, IE/Edge, and Chrome are all made by large corporations concerned more with molding the web to their own needs/profits that with the fate of their users. Even after Edward Snowden’s revelations, many still cling to these locked down proprietary browsers. I honestly do not understand it.