Few people realize when a browser draws the borders, it draws them at angles. This technique takes advantage of that. One side of the border is colored for the color of the arrow, and the rest are transparent. Then you set the width of the border to something large, the ones above are 20px. To demonstrate here is a div with all sides colored.
I knew they were angled; but never would I have thought to do this with that knowledge.
Site generated weird message about storing data for offline use. Was a bit of a huh?
love the js resource list as well.