Powerful plugin that lets you redirect error pages from within the WordPress admin to the new pages you’d like them to go to. Video will show you how it’s done. Just the basics here, the plugin can do quite a bit more. Careful, if you get page “confusion” errors (where you think it should be loading one page but it’s loading another, check the logs and poke around in the plugin as maybe something is redirecting that you don’t want to).