Ah, yes. Apple seems to almost spitefully change document URLs on a regular basis too. (Which would be a little less terrible if you could simply re-Google the replacement link but you can’t.)

My favorite experience was looking for virtual key codes. A few years ago, there was a point where the only place you could find the values of (arbitrary) virtual key codes for input events was in a printed copy of Inside Macintosh for System 7. Was this some ancient Mac? No, it was needed on OS X, by their “preferred” Cocoa/NSEvent no less, and their modern hardware was sending the same codes. They eventually “fixed” this by putting the information inside Carbon.framework header files (which will most likely just disappear in the next OS update).