For the Online Battlefleet Gothic: Remastered Rulebook, I wrote a script to check all the internal links to make sure that none of were broken. mkdocs, the tool that I use to maintain that site, very helpfully reports on any Markdown links that are broken, but it can’t do much with links to non-Markdown URLs, and links written in HTML. Hence the script.
Having written it, In turned it on this site, and found a whole bunch of broken links, some dating back more than fifteen years! This site has lived on many different platforms (self-hosted PSG, Wordpress.com, self-hosted Wordpress and finally self-hosted Jekyll) and a bit of link rot has been introduced with each migration. Hopefully those are all fixed now.