DOCTYPE present
What the check finds
No DOCTYPE declaration, which puts browsers into quirks mode. Rendering may differ from what the page intends, though parsing still works.
Why it matters for AI answers
Without a DOCTYPE, browsers use quirks mode and layout may differ from what was designed. Crawlers still parse the text, so the effect on AI answers is small.
How to fix it
- Add <!DOCTYPE html> as the very first line of every page.
- Check the page layout in a browser after the change, since leaving quirks mode can shift styles.
Related checks
Review this finding in context: Security and technical hygiene guide ›
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