404 Error - Meaning of 404- SEO Basics - Learn SEO

When we expand the code 404, the first digit “4” represents a client error. The server indicates that you did a mistake like misspelling the URL or requesting for a page that is no longer available.

The middle digit, 0 represents a general syntax error and could indicate a spelling mistake.

The last digit, 4 refers to a specific error in the group of 40x.

The Error 404 "Page not found" is the error page displayed whenever someone asks for a page that’s simply not available on your site. As there is no web page to display, the web server sends a page that simply says "404 Page not found". It is an HTTP (Hypertext Transfer Protocol) standard status code.
The default 404 error page as shown on Internet Explorer is given below.