404 code (also known as the "page not found" code) is a standard server http response when it has been asked for a resource (such as a page or image) that it can't locate. It means that the page you've requested is not there. Used as a verb (such as in the sentence "I 404'd the page.") it means you had a page, but took it off the server so that anyone looking for it now only receives a 404 code that the page doesn't exist. Your request isn't being routed to a replacement page using a 301 or 302 code. It means the page you wanted ceased to exist, or never existed in the first place.
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