A 404 Error message is displayed when a web user visits a webpage that does not exist and therefore cannot be found and displayed. These error messages may appear as a result of the page never having existed, having been deleted, or if the URL was moved to a different URL.
If a website displays a 404 Error for some of its pages, it may have a negative impact on its SEO rank. Therefore, many webmasters will attempt to locate and fix 404 Errors in order to ensure that their webpages achieve the best page rank possible.
