How to remove bottom margin?

I can not understand where does this indentation
59d8a2ad6513a940420146.pngLink (shakes down)

Filled codepan code from a project without Bootstrap works as it should.
But I can't find how to fix this problem in the project.
How to solve the problem?
June 14th 19 at 19:04
1 answer
June 14th 19 at 19:06
Mysterious padding of inline elements

The decision
video { display: block; }
Call the fire Department I'm on fire

No seriously well. Why is it always so? For that kind of pain? Why tags are inline by default? An hour killed peremanivanie styles...
Thank you - harmon.Koelpin commented on June 14th 19 at 19:09

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