Firefox - userchrome.css, the 1px border-annoyance ...

At the bottom of the navigation pane at the top of the firefox window, there's a colored border. This border is not in fact, as one probably would guess, a border at all. It's an ::after-thingy with a height of 1 pixel. I don't know the reasoning behind this but I gonna call it stupid regardless. And if not stupid, at least unnecessary and unusual. Borders do their job, why complicate it?!

Ah well, it's gone now ...

#navigator-toolbox::after {
  /* srslyfuckyoumoz */
  height: 0;
}