A 404 error is the 'page not found' message visitors see when they land on a web address that doesn't exist on your site - usually from a broken link, a deleted page, or a mistyped URL.
Also known as: Page not found, broken link
In plain English
Every page on your website lives at a specific address. When someone (or Google) requests an address that isn't there, the server answers "404" - it looked, found nothing, and is telling you so. It's the website equivalent of knocking on a door that isn't there.
Why it matters for your business
A handful of 404s is normal. A page full of them means visitors hit dead ends, Google wastes its crawl budget on missing pages, and it can signal that content was deleted or URLs changed carelessly. Fix the links or redirect the old addresses.
When you'll run into it
After deleting or renaming pages, changing your permalink structure, or when an old marketing link points somewhere that no longer exists.
Run into this on your site?
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