Units of Measurement

CSS units fall into three groups:

1. Absolute – px, pt, cm, mm, in (rarely used for responsive layouts).
2. Relative – em (relative to parent’s font‑size), rem (relative to root), % (relative to the parent element’s dimensions).
3. Viewport – vw (1 % of viewport width), vh (1 % of viewport height), vmin, vmax.

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Example: Full‑height hero section

.hero { height: 100vh; }