Today I was re-reading a PDF I downloaded in 2016. The broken link on the last page went to the 404 page on the author’s website. Surprise! It was not optimized.
I’m a long-time fan of this influencer, so I sent him a link to Neil Patel’s mammoth article with 12 examples of how to do this. If you’re a blogger or store owner, add Custom 404 to your Pages checklist.