The "Correct Use of the Apostrophe in the English Language" page claims that the rules are "very simple". If they're that simple then why do you need 8 bullet-points and five screens of text to explain these "very simple" rules?
I wish people were more relaxed about this kind of thing. Just accept "its" and "it's" as correct, and "Two week's time" and "Two weeks' time", etc. No one gets confused by this sort of thing.
Our brains are geared towards spoken language, not written language. My main take-aware from this is that we should change the spelling to be less error-prone, or just accept both as correct. The problem is with the spelling, not the people.