CSS

Match the element you mean before adjusting its appearance.

Understand where an element’s width really comes from.

Find out why your declaration is being overridden.

Arrange navigation and controls along one main axis.

Let a collection of cards find the number of columns that fits.

Let the layout respond to available space and readable content.

Keep repeated design choices in one readable place.

Use transitions to explain a change, and respect reduced-motion preferences.