Ranker.com now as a pop-under message at the bottom of the screen that Ad-blocker Plus won't block. Anyone have an idea how can I block this very annoying pop-up? Every time the page reloads, the pop-under returns.

It has four boxes that read: Share, Tweet, Pin, Email.

For Adblocker Plus to address the situation will require their recognition of the issue and dealing with it in their next update (should they choose to do so).
Keep in mind that they last updated (to version 2.6.3) in early June, so it may be a while.
You could always drop them a line.

Speak of the devil (or devel?):
Adblock Plus just updated to version 2.6.4, although it may have affected only the filter list(s).
See if it helps.

True, but that didn't solve it. I couldn't figure this one out. Not urgent.