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Source-reading note: the exact semantics here come from the HTML element/attribute you chose, not its CSS appearance.
Engineering judgment: prefer the native HTML behavior described here before reaching for a custom widget.
When this goes wrong, the browser usually keeps rendering. That is what makes the bug easy to miss: recovery can hide a broken source document. In this lesson, the focus is the accessibility tree, semantics, source order, and user needs. That matters because HTML is interpreted by a parser and then exposed to browser features such as navigation, accessibility tooling, form controls, media handling, and script APIs. A correct-looking screenshot can still hide a poor document model.
<main><h1>Order status</h1><p>Shipped yesterday.</p></main>
Native semantic HTML gives browsers accessibility information that can be consumed by assistive technology without authors inventing equivalent ARIA roles.
Start with the smallest meaningful example. The working snippet demonstrates the core syntax, but the important part is what each piece contributes: the element supplies semantics or behavior, attributes refine that meaning, and surrounding structure gives the browser context. Don't add markup just because a framework or copied example happens to include it.
<button type="button" aria-expanded="false" aria-controls="filters">Filters</button><section id="filters" hidden>...</section>
Native semantic HTML gives browsers accessibility information that can be consumed by assistive technology without authors inventing equivalent ARIA roles.
<img src="chart.png"alt="Orders increased from 120 in May to 190 in June.">
In a team codebase, the expensive bugs usually come from assumptions. Someone assumes an anchor is just a button with a different visual style, that a placeholder is a label, that an iframe is only a rectangle, or that a client-side constraint is security. The safe engineering move is to name the browser behavior you actually depend on and encode it directly in HTML.
Implementation note: Start with native HTML and identify where the browser already exposes useful semantics to assistive technology. Keep the browser behavior observable while you work.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.