Modern CSS & HTML

Write CSS and HTML with current platform features. Prefer native materials over legacy hacks and unnecessary JavaScript.

Composition with other skills

• This skill owns native implementation choices.
• fluid-design owns interaction feel when physics, interruption, or gestures exceed CSS.
• semantic-html-first owns element and ARIA boundaries.
• If a native CSS/HTML feature can meet the requirement with acceptable support, use it.

Browser support policy

Target features available in both WebKit (Safari) and Blink (Chrome/Edge) unless the task explicitly allows a single-engine experiment.

• Widely available in both engines: ship as default.
• Newly available in both: ship with @supports / progressive enhancement.
• Single-engine or unstable: mention as optional; provide a cross-engine path.