I swear Firefox (iOS, so could be a WebKit thing?) starts tabs scrolled down below the page header recently. Definitely happens on HN now and then (although typically I can't recreate it right now..) pretty sure I've seen it elsewhere too.

I wonder if that is a) actually true browser behaviour and not something the site itself is doing (or something I've managed to make up)

b) if a is true, the reason it hid the kinda-header-looking text representation of the images from OP

Unfortunately I'm at a loss for the keywords to search to confirm this behaviour, I'm only able to find unrelated scroll/header results