Just pulled up some documentation for the String class again today (perhaps I'll eventually commit the entire contents to memory, but today is not that day), and noticed that Salesforce is rolling out a UI change for the documentation. Arguments about the intersection of information density and typography aside, there has been a change to the URL structure as well.
Looks like "apexcode" has been replaced with "apexref"
Looks like the old URLs are set to redirect to the new ones, at least for the time being, but yeah, prime example of "links tend to change or go dead over time".
Not much to discuss here, I don't think. Just wanted to share the knowledge and suggest we update the canonical-qa resources.