404 (not found). 500 (internal server error). Types of HTTP status codes HTTP status codes are divided into five different categories that give you a peek into how your request was handled: ...

The 4xx range of status codes functions largely as expected. Google appropriately processes standard codes like 404 (not found) and 410 (gone), which remain essential for proper crawl management.

If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead. Google warned once before about misuse of 403s on your site.