Your HTML file opens blank, shows as text, or downloads instead of rendering. Check the extension, the file:// open path, the doctype and a missing closing tag before you rewrite the page.
Measure two boxes with the same declared width, calculate padding and border, and reproduce the 100% width overflow mistake before fixing it.
Compare text alignment, a centred block and two-axis child placement, then test why centering needs available space.
Diagnose an ID rule that defeats a reusable note modifier, then keep the ID for navigation while moving presentation to classes.
Set a shared typography base, trace inherited colours and remove a local override without restyling every paragraph.
Trace a reproducible colour and spacing conflict from the rendered result to the winning rule, then verify the repair in the source file.
Build a local form with working labels and a grouped topic choice, then inspect submitted field names without sending a message.
Choose different text alternatives for informative, decorative and linked images, then inspect their names and broken-image behavior.
Build a three-file local site, resolve paths from nested folders and test fragments and deliberate new-tab navigation.
Build a page with named navigation regions and a working skip link, and distinguish page landmarks from an article header.
Reuse one card across home, catalog and related-item contexts, test long content and keep each action accessible without nested links.
Reproduce a fixed-width overflow on a narrow screen, locate the offending element and verify a repair without clipping the page.