Check whether each HTML primitive actually provides the behavior a feature needs.
Review the contracts
- HTML base: change how every relative URL resolves
- HTML complex tables: connect each value to all applicable headers
- HTML popover: show dismissible nonmodal help with a button
- HTML declarative shadow DOM: parse a component boundary from markup
- HTML canvas: draw a chart without hiding its underlying data
- HTML dialog versus popover: decide whether the task blocks the page
Common Mistakes
Markup never creates missing server routes, assets, permissions, or saved state.