Fundamentals Css Questions

See exactly how border-box redefines the width property, why it makes layouts composable, and where it can still bite you.

Understand the four layers every element renders as, and how the two box-sizing modes change what width means.

Learn where each lives in the box model, how their behaviour diverges, and the concrete cases where swapping them breaks a layout.

Understand the three collapsing cases, why parent-child collapsing surprises people most, and the modern ways to stop it.