>>> My Info: Win7_64, Nightly 53, 32bit, ID 20161119030204 (2016-11-19) STR_1: 1. Open http://coub.com/ 2. Start autoscrolling (not too fast), sometimes moving mouse above the videos AR: Videos become partially clipped while <video> elements are fully visible on the page ER: No clipping STR_2: (detailed) 1. Open http://coub.com/ 2. Middle-click ~100px to the right and to the top from the 1st video on the page, move mouse down by ~15px to start autoscrolling 3. Move mouse horizontally to hover mouse over the 1st video 4. Move mouse horizontally to place it on the same horizontal coordinate as autoscroll circle +-5px 5. Repeat the same with 2nd and 3rd videos This is regression from bug 1313898. Regression range: > https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=0005d0bfadf72746ce36f4e8d09d9504b814557e&tochange=ba20391edbec448b56725ef01158176614706b4f@ C.J. Ku[:cjku](UTC+8): It seems that this is a regresion caused by your change. Please have a look.

Hi arni2033, Sorry, I do not fully understand what's "autoscrolling" here. Does that means you scroll the page by wheel?

(In reply to C.J. Ku[:cjku](UTC+8) from comment #1) > Hi arni2033, Sorry, I do not fully understand what's "autoscrolling" here. Does that > means you scroll the page by wheel? Autoscrolling is basically what STR say. You can scroll by rotating mouse wheel (scrolling) or moving mouse with middle mouse pressed (autoscrolling). Video: https://www.youtube.com/watch?v=6_8tbkfrHRQ Also, this seems to be only reproducible on Nightly 2016-11-19, but not on Nightly 2016-12-29. So, just close this as "resolved worksforme".

thanks