Thanks for spending time to let me know because I don't think I would have noticed it otherwise! I can't see it on retina but I can on my non retina display. We'll have to make the CSS rule more specific. As to why it's there I believe Firefox 57 or around that version had an issue with the sliding animation on the top of the page causing images to tear or not render at all when they scrolled in. This bug must have been solved recently because disabling backface-visibility on the image doesn't cause the same tearing.