Today I read a short article on a subject I knew at one point, but feels fresh to remember.

The article was Meet border-box, my best friend.

It describes the difference between box-sizing: border-box and box-sizing: content-box.

Basically, content-box means that only content (and not padding & borders) use the height & width values on the element.

When border-box is the value for box-sizing, a div that is set to say, width: 200px and has a 6 pixel border will actually be 200 pixels from border edge to border edge, not 212 pixels like it would be if you were using content-box.

Good reminder!