Why does the block move down when text is added to it?

Question

css

When you add text to any of the blocks, it will blend down. Please explain what's the matter?
link

Answer 1

jsfiddle.net/oekq71yg/1

Answer 2

add to an empty block  
or vertical-align: bottom; in divs,
as I understand it, inline-blocks without text are rendered incorrectly. to solve the problem, add vertical-align: bottom;

Answer 3

This is because the header has a margin by default. Reset it and that's it.