Firefox Android Icon in Address Bar

[insane42]

The one thing I've always hated about Android and many of its applications, is the lack of detailed usage instructions. I never could find a simple explanation of what all the icons the Gmail app did....

I've looked through the FAQs and did some searching, but I can't find an answer.

What is the little Android Icon that sometimes pops up in the address bar on the latest Firefox? It comes up right next to the reader icon on most non-mobile pages. Any time I tap it, it just says it can't play the video. Umm, what video?

Anyone know what it's for?

Thanks!