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Why HTML validation errors matter

Best practices1 min readFixes check html-valid-errors-count

Browsers repair broken HTML silently, but each repair is a guess and can differ between browsers and crawlers.

Step by step, with screenshots: HTML validation errors: which ones matter and which are noise →

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What a passing site looks like

  • No HTML validation errorsinfo onlyeffort M

HTML validation errors

Why it matters. Invalid HTML usually still renders, but each error is a place where browsers, screen readers and search engine parsers may disagree about what you meant.

How to fix it.
  1. Run the page through the W3C validator and fix unclosed tags, duplicate ids and misplaced elements first.
  2. Ignore warnings about vendor attributes if the page renders correctly everywhere.

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