@searchguru
Re: it's and it's: The reason that spell check isn't doing what you expect is that it's is an abbrviation of it is wheras the possessive term is actually "its" not "it's", as in "its mine".
@AO, "Doesn't all this brujaja boil down to horrendously lasting influence of the medieval English grammarians who, convinced that Latin was the purest language, decided that English could be analyzed according to Latin grammatical paradigms? "
I don't think that the current greek/latin root confusion dates back to medieval grammarians but to Dr. Johnson, the author of the first English dictionary, who decided which words he thought had Latin roots and which had Greek (often very badly). It's (not its!) all been downhill since then.
For some excellent writing on the origins of the English language and its correct use see Bill Bryson's "Mother Tongue" and "Troublesome Words" and also "Eats, Shoots and Leaves" by Lynne Truss regarding the reils of punctuation.
Bill points out that the assumption that it's (not its) correct to use an "S", not a "Z", is a common misconception in the UK and that many spellings with z in can be traced back some considerable time; i.e. before the Americans decided to standardise all the spellings in bizare ways. (E.g. Color, not colour, armor not armour, etc.) From this you can tell I'm English not American. (I'd have gone for culler, armer or armur, etc.!)