This report displays pages with status code 404 - Not Found.
A 404 error page tells search engines that a page is not found. This happens because you may have changed your URLs over time, removed a few pages when you overhauled your website design, or linked to a third party page (not knowing they changed the URL or moved the page).
404 errors don’t negatively impact your SEO in terms of ranking, but if there are so many that your website is being abandoned by frustrated users, you may not continue ranking so well. Search engines don't tend to rank pages that provide a poor user experience. It is important to have customized 404 pages with recommended navigational options when website visitors request pages that return a 404 response code.
Note that using this report requires configuration (See how to configure SEO reports).
Available Report Widgets
The Content Not Found table widget contains the following columns:
Title – The title or URL of a page or document
Status Code – Not Found
Linked By Count - Linked by count is the number of pages which link to this page