404 Error — Definition
A 404 error is what a browser shows when someone requests a page that doesn't exist on your server — either because the URL was mistyped, the page was d...
What it is
A 404 error is what a browser shows when someone requests a page that doesn't exist on your server — either because the URL was mistyped, the page was deleted, or a link pointing to your site is broken. "404 Not Found" is the technical response code your server sends back.
Why it matters
404s are dead ends. A visitor hits one and they're done — they either go back or they leave. Too many 404s also signal to Google that your site isn't well-maintained, which can affect how much of your site gets crawled and indexed.
The mistake most people make
Having a generic, unhelpful 404 page. If someone lands on a 404, you've already lost them a little — but a good 404 page with a search bar, popular links, and a human message can recover some of them. A white page that just says "404 Not Found" recovers nobody.