As the title says, when on Fullscreen, the bottom part of the taskbar is visible, and I can even click on to it to make the taskbar appear on top of firefox. Clicking anywhere on firefox makes it disappear again, but still leave that thin strip of the taskbar visible. I have checked different browsers, including Chrome and Cyberfox, and this issue exists only on Firefox and Cyberfox (since they are essentially the same). In any case, Firefox is my main browser, and this is what I am interested in fixing. After some digging, I found out that if I lower my DPI setting, this issue goes away. At all DPI settings from 100% to 125%, there is no issue. But at 130% (which is my preferred setting) the blue line of the taskbar appears. I have changed the color of the theme, to change taskbar color, and the thin line also changes color. I tried hiding the taskbar, using Windows' "auto-hide taskbar" feature, and in this case I see the top of the taskbar, as opposed to the bottom! Again, this is a Firefox only issue (Cyberfox is still a modified Firefox), all other browsers, Chrome, IE, etc are fine. I am interested in any solution that might work. The reason that this visible persistent thin line being annoying, is that it appears on fullscreen youtube videos, as well as all fullscreen videos, and its most noticeable on dark videos or videos with black bars on the bottom and top. Thanks in advance P.S. You have to view the attached image in fullscreen to notice the blue line at the bottom. Its very thin, so either fullscreen or zoom in.