I see it everywhere, not only in emails and blogs, but also in professional publications. It's driving me crazy with its ubiquity.

It's very simple. I don't know why it's and its give writers so much trouble. Well, check that, I do know most of the reason -- it's because when we want to make a word possessive, we usually add an apostrophe before adding the final S "That book is John's." "I'm going to Grandma's house."

But IT in the possessive does not add the apostrophe. "The car went its fastest." "The school raised its scores." Possessive IT - NO apostrophe.

IT'S is only for contractions. That is, turning two words into one. It is = It's. "It's a crying shame." ... It has = It's. "It's always been that way."

So, if you mean something that belongs to IT, use ITS. If you mean IT Is or IT Has -- if you can say what you mean using those two word combinations -- use IT'S.

It's beautiful in its simplicity.

Guide to apostrophes

Step One: Standing In

The apostrophe's first job is to stand in for a letter which has been removed for the sake of convenience, such as when where is becomes where's. These words are known as contractions.

For example, “That is a nice frock, dear,” becomes “That's a nice frock, dear.” That is has been contracted to that's and the apostrophe is standing in for the letter i.

Step Two: Who Owns What

The apostrophe's second job is to indicate who owns what in a sentence. This is called a possessive apostrophe and can either be singular (something belongs to one person or thing) or plural (something belongs to a group). The easiest way to show how it's used is with a few examples.

Harry's books are on the desk.
The apostrophe shows that the books belong to Harry.

The bird's eggs were gathered from the nest.
The apostrophe shows that the eggs belonged to the bird.

If the eggs belonged to several birds, the apostrophe would move:
The birds' eggs were gathered from the nests.

The children's books are on the desk.
The apostrophe shows that the books belong to the children.

Note: the apostrophe goes before the s because the word children is plural. If you put the apostrophe after the s, the books would belong to the “childrens”, which is nonsense.

Step Three: Its and It's

This is one that people often get wrong but it's simple if you remember this: If you mean it is, use it's. Otherwise, use its.

It's is a contraction, a shortened form of it is.
It's a nice day. It's no good remembering things the day after the exam. It's a long way to Tipperary.

Its stands in for a noun in a sentence to prevent repetition.
The cat chased its tail. The business said its results were brilliant. The dog ate its dinner.

Without its, we'd have to say the cat chased the cat's tail, the business said the business's results were brilliant and so on, which is clumsy and repetitive.

All Done

So that's it. Apostrophes in three easy steps. Why not bookmark the page so you can come back and refresh your memory from time to time. Meantime, go forth and punctuate.