404 error

What it means

A 404 error is a server response saying the requested page does not exist. It occurs when someone opens an address that was deleted, moved without a redirect or typed incorrectly.

Having some 404s is normal, and search engines read them as a sign the page has been removed. The problem arises when internal links, links from other sites or customers' bookmarks point to non-existent pages.

When content moves to a new address, a permanent 301 redirect should replace the 404, passing both visitors and link value to the new page.

How it works in practice

Error pages are tracked in Search Console and by crawling the site. On large sites, many of them waste crawl budget because the search engine keeps revisiting dead addresses.

A well-designed 404 page should not be a dead end. It should explain what happened, offer search, links to the home page and key sections, and keep the site's look.

Before a redesign or migration, a map of old and new URLs and the redirects must be prepared. Otherwise the site loses part of its traffic and rankings after launch.

What to watch out for

Redirecting every missing page to the home page is a mistake. Search engines treat it as a so-called soft 404 and it confuses visitors; redirecting to the closest relevant page is better.

Watch out for pages that display „page not found“ while the server returns status 200. Search engines then index them as normal content and clutter the index.