CSS conventions

Follow the target repository's browser baseline, styling system, resets, tokens, and nearby patterns first.

Browser support

Inspect .browserslistrc, the browserslist field in package.json, and relevant build configuration before choosing CSS features, prefixes, polyfills, or fallbacks.
Treat the repository's declared browser targets as the compatibility boundary. Do not add workarounds for older browsers outside that boundary, and do not use unsupported features without the fallback required by browsers inside it.

Do not choose semantic elements for their default display; use <p> for paragraphs, <span> for inline text, and <div> for generic block containers.
Inspect global reset and base styles before adding local resets. Do not repeat margin, padding, or list-style resets already applied to the target element.
Reuse existing semantic design tokens and verify each referenced custom property is declared. Do not invent a token or a new size for every literal value.

Add min-inline-size: 0 or min-block-size: 0 only for demonstrated intrinsic overflow, Grid/Flex shrinking, native-control overflow, or 0fr disclosure collapse.
Explain non-obvious intrinsic sizing constraints with a short CSS comment at the declaration.