404 Error
In one line
A 404 error is the HTTP response signalling that the requested URL does not exist — affecting both user experience and crawl efficiency.
Going deeper
A 404 means 'this URL does not exist'. Some level of 404s is normal, but if a key category page or popular article is 404ing, you are losing traffic immediately.
Two practical levers: first, 301-redirect broken URLs that earned external links to a relevant live page so the equity is recovered. Second, ship a helpful 404 page with search and popular content links to keep users on the site.
Make a habit of reviewing the 'Page indexing' report in Google Search Console. A botched URL-structure change usually shows up here first.
Related terms
301 Redirect
A 301 redirect is the HTTP status code that says a URL has moved permanently — passing essentially all of the original page's link equity to the new URL.
SEO302 Redirect
A 302 redirect tells engines that a URL is temporarily redirected — search engines keep indexing the original URL rather than transferring signals to the destination.
SEOGoogle Search Console
Google Search Console (GSC) is Google's free tool for monitoring how a site performs in Search — impressions, clicks, indexing status and technical issues.
SEOCrawlability
Crawlability is how easily a search engine bot can reach and follow your site's pages — the precondition for indexing.
SEOLink Equity
Link equity (often called 'link juice') is the authority and ranking signal a page passes to another page through a link.
SEOSoft 404
A soft 404 is a page that has no real content — or shouldn't exist anymore — but still returns 200 OK, so search engines misread it as a thin but live URL.
SEOBroken Link
A broken link is any link that fails to resolve — usually 404 — and quietly degrades both user experience and crawl efficiency the longer it is left in place.