@Habbie Also check out 4042307.org by @aral, and all the tutorials about redirecting dead links to the Internet Archive's Wayback Machine!
I myself built a special script which gets the list of all previously existing URLs on my site from the Internet Archive API, checks if they still exist, and if not I add them to my `_redirects` file which specifies the archived URL to redirect them to. If you know how Wayback Machine links work you can even directly link to assets, without any GUI ("im_")