A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
Implementation note: Resolve sibling, child, parent, root-relative, and fully qualified URLs from a known page path. Keep the browser behavior observable while you work.
Checkpoint: you can now connect the markup for absolute and relative urls to a browser behavior and a concrete debugging step.
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 URL resolution, document base URLs, and path-relative addressing. 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.
<a href="../images/logo.svg">Logo</a><a href="https://example.org/docs">External docs</a>
The browser's defaults are part of the behavior you are learning. Prefer native semantics first, then test the exact combination of attributes and content you plan to ship.
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.
<a href="docs/start.html">Start</a><!-- On /products/2026/, this resolves differently than /docs/start.html. -->
The browser's defaults are part of the behavior you are learning. Prefer native semantics first, then test the exact combination of attributes and content you plan to ship.
<a href="https://example.org/docs" target="_blank" rel="noopener">Reference</a>
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.
Warning: invalid or overly permissive markup may still render. Rendering is not proof that the document model is correct.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.