How to hide the one-pixel leftover from the taskbar after activating the “Auto-hide the taskbar” option? [duplicate]
Solution 1:
You can't make it go away..
It needs a recognition area so it can spring up when you hover your mouse there.
It is unrelated to how your screen fits your monitor's resolution, unless you are still on an old CRT screen. LCDs ought to be used at 1:1 pixel resolution for best appearance.
You could possibly push your screen into overscan [at some quality loss] but you'd have to find that in the monitor's manual.