Frontend Syntax HTML5 Semantic

This skill fixes the choice of HTML element for every region and content type. It is built on the architecture position from [[frontend-core-architecture]]: the markup layer is the foundation, and native semantic elements ALWAYS beat <div role="..."> for accessibility tree mapping, focus management, and platform integration.

The skill targets evergreen-2026 browsers. The <search> element (Baseline Widely Available since October 2023) and <details name=""> accordion mutual exclusion (Baseline 2024) are treated as available without polyfill. Declarative Shadow DOM via <template shadowrootmode> is Baseline becoming Widely Available.

Quick Reference

Landmark elements and implicit ARIA roles