In very simplified terms, "404" is just a number that's included in the "invisible" HTTP header of the web page you're visiting. Whether this number is "200" (s

In very simplified terms, "404" is just a number that's included in the "invisible" HTTP header of the web page you're visiting. Whether this number is "200" (success) or "404" (not found), it doesn't affect how your browser renders the web page. Technically you could have a website where you serve real web pages full of content using the (wrong) 404 code, or serve web pages that tell the user "not found" using the (wrong) 200 code. It would massively mess up bots, search engines, browser extensions, and any other software that needs to know whether a page actually exists - but it would be fully browsable like normal by a human with a web browser, since humans don't see or read HTTP headers.