Ya know, I’ve always disagreed with this one. INO, when “it” is being used as a pronoun, and you are indicating possession, the word should be written “it’s” just like you would say “John’s” or “Mary’s”.
My computer lost it’s hard drive. My basketball lost it’s air.
You wouldn’t write “Johns computer” or “Marys basketball”, would you?
Well, it’s actually a quite regular rule apart from this exception: whenever pronounced, the clitic which casts phrases into the genitive is always written as 's, with no space separating it from the previous phrase…
EXCEPT when the previous phrase ends in the word “it”. In this case, and this case alone, forget the apostrophe.
An irregular exception like that, well, it’s no wonder people tend to forget about it. In a sense, to do so is merely to be consistent (precisely the sort of “logicality” business which the easily peeved tend to venerate, or at least give lip service to, in other contexts).
ETA: This is exactly the same point as Snowboarder Bo is making, but I didn’t see the above post when I wrote this one.
Hm… these actually do seem indistinguishable to me. Did you mean to interchange the apostrophe and the terminal <s> in one of these?
Also, I suppose I misread what you were saying in the bit I quoted in the above post; I realize now that you were talking about the case where, in casting a plural into the genitive, there is no change in pronunciation.
The same reason noone will find the word “noone” in the dictionary.
It’s two separate words, people.
Yes, it’s written as two words, but this is arbitrary. There was a time when “nowhere” was written as two words as well. It’s just the same phenomenon in action. (Indeed, there may even be grounds to support the claim that “no one”, in the relevant sense, acts syntactically as a single word, despite being written as two. Not that word boundaries are an entirely concrete matter…)
It’s obvously a big deal to you. I don’t think most people on the internet think they are being graded. I personally don’t think its a big deal. 
Although I basically agree with Snowboarder Bo’s position, I do have one question:
When is it not?
I mean I myself am often lazy and write without apostrophes or punctuation or capitals. But laziness isn’t an excuse for taking the extra effort to write an apostrophe in it’s or her’s or your’s or plural’s or third person verbs. I guess my biggest problem is too many apostrophe’s, and it’s is just one example of that.
This is a good thread to bring up another common mistake I see everywhere, including all over this board.
“The people WHO” not “The people THAT”
When I made the mistake, it was because I thought the possessive apostrophe applies to everything. Except, it turns out, for the word “it”. And for a long time after learning that weird fact, I still didn’t know why it was that way, so continued to occasionally make the mistake.
Until someone pointed out that “its” fits in the same category as “hers” and “his”.
I should not have used the clumsy phrasing “possessives that end with s.” That was my way of excepting the personal possessive pronouns. (my, your, etc) I was actually trying to say the same thing as both you and Airman Doors.
With that last bit, I was comparing this to a similar phenomenon, that people often think possessives must end in 's, to the point where students, when shifted into the genitive, becomes student’s instead of the more proper students’.
I offer another phenomenon as a hypothesis: that many people do not know which homonym is supposed to be used in a given situation. I offer Khendrask’s examples as evidence.
In fact, even though I know which is which, I’ll often type the wrong one, and have to correct myself. It’s as if I’ve become habituated to using a particular spelling for a particular set of sounds.
An argument was posited above that this spelling convention (which, in my opinion, is largely arbitrary, simply to distinguish the genitive marking of it from the contraction of it is) is logically explained by an analogy between its and other pronouns’ genitive (i.e., “possessive”) markings.
Note, though, that there are THREE senses of its with genitive marking which we may consider, parallel to my/her vs. mine/hers vs. me’s/her’s (yes, this exists, via phrasal genitives; you’ll see).
The sense parallel to my/her is most obvious; “My/Her/The dog’s/Its name is rather long”.
The sense parallel to mine/hers is not so hard either: “If you only remember one name tonight, remember mine/hers/the dog’s/its.”
Finally, we can also consider a phrase like “The woman standing next to me’s dress”, as used to refer to a dress belonging to the woman who is standing next to me. This is indeed perfectly grammatical, and it would not at all do to substitute my for me’s (without switching parsing and thus changing the meaning; and substituting mine would be even worse, being ungrammatical on any parsing). So there are situations in which one has me’s, and him’s, and her’s, and all the rest of it. “The woman standing next to me’s/her’s/the dog’s dress”. Just as well, we can substitute it. “The woman standing next to it(’)s dress”. In this, with the meaning of the dress belonging to “the woman standing next to it”, would one write its or it’s? If still the former, then this would entirely be unaccounted for by any putative analogy between “its” and “his”. (However, I actually would, in my own writing, go for the latter in this situation, I think)
At any rate, any argument purporting to give a logical reason for why its should be spelt with an apostrophe has to cover not just the first case, but the second case as well, as well as the third case (either by explaining why the third case should also be spelt with an apostrophe or why the third case is different enough to not need to be spelt with an apostrophe, depending on position taken).
I don’t think most people on the Internet know much of anything.
Just remember that the ONLY time “it’s” has an apostrophe is when you are using the contraction of “it is”. Any other time, if you are using the possessive, use “its”. (Yes, I know I’m supposed to put the period inside the quotation, but I’m trying not to confuse things.)
Unless It is actually someone’s name as in “Cousin It’s hair is very long.”
You wouldn’t write “hi’s computer” or “her’s basketball” either.
Alright, but note that this position would destroy the argument that “its” is spelt without an apostrophe by analogy to other pronouns. For, with other pronouns, we would write “The woman next to me’s dress is beautiful” or “The woman next to him’s dress is beautiful”, but for one word, and one word alone in the entire written language, we are supposed to write “(The woman next to it)'s dress is beautiful” as “The woman next to its dress is beautiful”.
Which is fine, but if this is the position taken, then do recognize that it is an arbitrary convention, done only out of a desire to keep some particular homophones spelt distinctly, even in a situation where consistency in the rules would otherwise have them spelt the same. Which is all the more reason not to be upset that some fail to memorize or pay attention to this corner-case exception, and re-regularize the rule-following in their own orthography.
No, because “his” and “her” are both pronouns which include possessiveness. Or did you have some point you were trying to make?
For the same reason the sign reads
DONT
WALK
and not
DON’T
WALK
I know the difference. I even know I am doing it, when I do it.
I simply dont care.