If this isn't a targetted advert in my browser, I don't know what is.
And here's where you turn it off:
Sure. User.js is a file you can add in your Firefox profile directory which gets loaded each time Firefox starts.
Pretty good documentation here: https://kb.mozillazine.org/User.js_file
The arkenfox one is a fully loaded pro-privacy user.js made by some knowledgeable people. I did use that one for my initial version iirc: https://github.com/arkenfox/user.js/blob/master/user.js
How often do I update it? Just when mozilla rolls out a new feature I don't like. I commit it to my repo, that way I easily take my settings to each different machine. You cannot change every FF setting with that file, but you can change the majority of them.