wpbeginner has a list of their favorite WordPress 404 pages. There are some good ones in there, but none of them do what I think they should do—that is, as well as provide helpful links to popular pages, also provide a list of guesses about where the user was actually trying to go. Coincidentally, today I also read this excellent article about finding the longest common subsequence between two strings. So, at some point, I’ll improve my blog’s 404 page so that it calls, probably via asynchronous request, a Python script that checks the user’s requested URL against all valid URLs WordPress knows about, and then suggests to the user whatever the closest matches are. I’m somewhat surprised that this isn’t done more often, but it seems that far too many sites are really blasé about 404s.