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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.
A useful way to learn this is to start with the browser's observable behavior, not the tag list. In this lesson, the focus is ul, ol, dl, nesting, and semantic list structure. 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.
<ol><li>Install<ul><li>Node.js</li><li>Editor</li></ul></li></ol>
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.
| Decision | Why it matters |
|---|---|
| Native element | Carries browser semantics and default behavior. |
| Attribute | Refines the element without replacing its meaning. |
| CSS/JS hook | Adds presentation or behavior around the existing structure. |
<!-- Contrast the weak version --><div>Lists and Nested Lists used as a generic container</div>
Don't confuse browser-side convenience with a security boundary. The markup in lists and nested lists should improve behavior, but authoritative validation and policy belong at the trust boundary that processes the request.
Now put the same idea under pressure. A realistic failure is: Represent ordered steps, unordered sets, and term-definition pairs without styling one element into another. 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.
When you debug this in a real project, inspect both the source and the parsed DOM. The two are related, but they are not always identical.
Implementation note: Represent ordered steps, unordered sets, and term-definition pairs without styling one element into another. Keep the browser behavior observable while you work.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.