Why it matters
Google only indexes URLs served with 200; 4xx/5xx pages are dropped and AI crawlers log them as wasted fetches. This is a scoring gate.
How to fix it
Serve the page with 200, or remove links/sitemap entries pointing at it. In Next.js, call notFound()/redirect() only for URLs that really are missing or moved.
References
More seo rules
void seo reports 60 rules in this category. What search engines need from the raw response: status codes, titles and descriptions in <head>, self-referencing canonicals, one h1, crawlable links, Open Graph, icons, robots.txt and a sitemap with real dates.
redirect-chainURL reaches its content through more than one redirectredirect-temporaryTemporary redirect (302/303/307) usedclient-redirectRedirect done with meta refresh or JavaScriptnoindexIndexable page carries noindexrobots-snippet-restrictednosnippet or a very low max-snippet limits previewssoft-404Missing page returns HTTP 200 (soft 404)html-too-largeUncompressed HTML is over Googlebot's 2 MB fetch limitrsc-payload-ratioInline RSC flight payload dominates the HTML