Validate HTML against W3C standards

Invalid HTML causes unpredictable rendering across browsers, breaks accessibility tools, and makes debugging significantly harder.

Quick Reference

• Use validator.w3.org or browser extensions for validation
• Fix errors first, then warnings (errors cause rendering issues)
• Integrate validation into CI/CD with html-validate
• Common issues: unclosed tags, invalid nesting, missing attributes

Check

Validate HTML markup using the W3C HTML Validator to identify and fix markup errors that could cause cross-browser compatibility issues.

Fix

Run HTML through W3C validator and fix reported errors including unclosed tags, missing attributes, and invalid nesting.