It’s often too easy to make edits to your web site that result in a broken link. This plugin will automatically email the web site administrator (or a specified email address) whenever a 404 is encountered, along with a link to the page the 404 originated from. With this knowledge in hand, you can search the page for the problem and either remove or fix it.
Notifications are also triggered by missing media, such as images, video, CSS files and more.
Report any issues at the official 404 Notify Support WordPress page.
How to use
Once activated, notifications are automatially sent to the site administrator, or, you can specify an alternative email address in Settings -> General and look for the 404 Notify email address field.
Deactivate the plugin, delete if desired.