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. Some shared hosting providers intercept 404 errors to provide their own custom error pages. Unfortunately this interferes with WordPress and causes raw html to be sent to the browser. This plugin changes 404 errors to 301 errors and redirects to a known page. So you can display your own custom page instead of display 404 error page.