What Elements Are Focusable?
This document is a testing ground to identify what a browser deems focusable and tabbable.
At first the document will add focus event handlers to every descendant of <body>.
It will then try to .focus() every element to identify which elements satisfiy Focus Managemenet.
After that you - the user - can hit TAB a couple of times (like 250 or something) to determine the browser's natural tabbing order
