I created a test page: http://www.davehylands/test.html The tiled background stops tiling around Line 909 (running Firefox 30) I did some calculattions, and the artifacts start around pixel 32768 (67 repeats of the 484 pixel high image = 32428 + a big more of the 68th repeat) Under Nightly 33.0a1 (2014-06-25) (the background shows up, but there are significant artifacts in the text and the image is shifted. On my Linux machine (Ubuntu 14.04) I initially don't see any artifacts (running Aurora (32.0a2 (2014-06-25) I can scroll all the way to the bottom and things look good. But if I scroll back to around line 2811 and then move up and down with the scroll wheel on my mouse I start to get artifacts. Under linux, I was able to get artifacts around line 948 sometimes (but typically around line 2811). Usually when scrolling backwards using the mouse wheel.

And I don't see any artifacts on my B2G Flame, running master, nor on my Nexus 5 (Android) running Aurora.

I see it on Ubuntu 12.04, with the "go to the end and then scroll back up". There is a "ripple" effect, probably from buffer rotation and some kind of precision. I'll see if I can get a regression range.

There is 29 as well.