Debugging CSS Grid Layouts With Firefox Grid Inspector

You may have heard quite a bit of talk about a CSS feature called “Grid” this year. If you are someone who cringes when you hear the words “CSS” and “grid” in the same sentence, then I highly suggest you check out this new CSS module called CSS Grid.
Browsers render HTML elements as boxes according to the CSS box model, and CSS Grid is a new layout model that provides authors the ability to control the size and position of these boxes and their contents.
Source: Smashing Magazine