dark horizontal line across my dock

atitprosper wrote:

For a week now, I was watching a video with my macbook pro. I later saw a dark horizontal strip/line across my dock. I put the computer off and later put it on. The line disappear upon restart but after some 20 minutes, the lines came back. Since then, if i put the PC off, the line disappears and after 20 minutes it comes back again.

What should I do?

You do not say what exact Mac /model /year /size /retina /touchbar is this ?

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"—

https://www.apple.com/retail/geniusbar/

outside the USA

https://locate.apple.com/country

From iOS app online Genius Bar appointment:

https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8

I suspect the beginning of a hardware failure with the Display. Take it to an Apple Store or Apple Authorized Service Provider to be checked out.