Trying to watch videos livestreaming on Firefox. The “box” part of the page which should show the video is completely black apart from a narrow band across the top of the box. This band shows part of the video which should be there. When I scroll the whole page up, the video picture, such as it is, seems to scroll at a faster rate than the page itself. The problem is not confined to one particular website. It occurs on any website on which I tried to watch a live streaming video. Clearing cache won’t help. I’ve only just started so there is no cache to clear. Thank you in anticipation. Jerry