404 Not Found Error
The 404 error comes in two types:
- a 404 occurs when the URL being requested does not exist
- a soft 404 occurs when a URL is requested and does not exist, but the server does not reply with a 404.
The latter is not particularly damaging to rank, but any patterns should be taken note of.
The 404 error usually occurs when a page has been moved, or renamed, or when the URL path structure has changed resulting in the page URL no longer existing after a given path.
Any tiny change in the URL of your page will completely reset any rank it may have gained, back to zero, so whenever moving a page to a different URL, consider carefully how this may affect your rank.
Large-scale changes to URL structures can be devastating for a website’s rank.
If a page URL is changed but the content is not, then you should set a 301 redirect to the new URL so that both users and Google know the new address of the page and can successfully re-engage in your content. Same-to-same content 301 redirection will retain around 90% of the original page URL’s rank, plus it will help preserve the connection of any backlinks to the old URL and redirect any traffic to the new URL.
If the change is permanent, consider trying to have the backlink corrected to the new URL instead of relying on the 301 redirect. 301 redirects should be kept in place indefinitely if you have evidence that traffic or crawlers are passing to the old URL.