So we check your 404 Page doesn’t have any errors itself, or cause any search engine index issues.
If a broken link sends a search engine or user to a 404 Error Page, that shouldn’t cause problems for your website. Unless your error page is broken itself, or sends a 200 Status Code by mistake. A 200 code indicates a successful result, not the 404 you would expect. And it’s easy to implement by mistake when you’re creating custom 404 pages for yourself or clients.
So we check the 404 page url and make sure you’re sending the right 404 Status Code to let everyone know that the page doesn’t exist. Which is as it should be.