I guess it can be considered a follow-up for Screen turned when writing answer - now when I write, random squares appear. Their coulor is
#042e4e as in
background-color:#042e4e; in site's CSS.
This time I took a screenshot:
Now, it happens only in FireFox, most recent stable build. Any ideas how to debug it? Happens only on Drupal Answers. Maybe someone is playing tricks on me or something? Or maybe it's Stack's incompatibility with FF? I have no idea...
It disappears on pretty much any interaction, so I wasn't able to track it with FireBug.