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You'll get more mileage from this topic by asking what information the markup communicates than by memorizing every attribute. In this lesson, the focus is scope, headers, captions, and choosing table markup for assistive technology. 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.
Warning: invalid or overly permissive markup may still render. Rendering is not proof that the document model is correct.
<th scope="col">Plan</th><th scope="row">Pro</th>
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.
Don't confuse browser-side convenience with a security boundary. The markup in accessible and semantic tables should improve behavior, but authoritative validation and policy belong at the trust boundary that processes the request.
<table><caption>Support queue</caption><thead><tr><th scope="col">Queue</th><th scope="col">Open</th></tr></thead><tbody><tr><th scope="row">Billing</th><td>14</td></tr></tbody></table>
Now put the same idea under pressure. A realistic failure is: Make relationships explicit enough for screen readers to announce meaningful coordinates. The browser may recover, ignore an invalid combination, or leave the user with a control that appears visually fine but behaves differently than expected. That is why source inspection and keyboard testing belong in the workflow.
<tr><th rowspan="2">Revenue</th><th colspan="2">Q3</th></tr><tr><td>July</td><td>August</td></tr>
For this topic, the edge case is worth remembering: HTML has legacy parsing and compatibility behavior, so invalid markup does not always fail loudly. If you are debugging a strange result, reduce the page to one element at a time, validate the source, and inspect the resulting DOM. Small reproductions beat guessing at the full application.
A small, explicit HTML decision now is usually cheaper than a compatibility or accessibility workaround later.
Implementation note: Make relationships explicit enough for screen readers to announce meaningful coordinates. Keep the browser behavior observable while you work.
Engineering judgment: prefer the native HTML behavior described here before reaching for a custom widget.
Engineering judgment: prefer the native HTML behavior described here before reaching for a custom widget.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.