Of all the problems in punctuation, perhaps the most common everyday confusion arises in knowing when to write “it’s”, with an apostrophe, and when to write “its”, without one.
Like a policeman, pesky apostrophes never seem to be around when you need one. And yet they always seem to turn up without warning when they’re not wanted, like an unwelcome Christmas guest.
The situation with “its” and “it’s” is actually very simple. You should only use an apostrophe if you are abbreviating the words “it is” or “it has”. For example, the sentence: “It is the best product the world has ever seen,” becomes: “It’s the best product the world has ever seen.” The apostrophe takes the place of the deleted letter “i”. When you then go on to explain that: “It’s got lots of flashing lights on its display screen,” an apostrophe is needed at the beginning of the sentence, where the meaning is: “It has,” but not toward the end of the sentence (because the statement: “It’s got lots of flashing lights on it is display screen,” makes no sense).
Bringing the apostrophe and the word “its” together often seems to cause trouble – but it’s really not a problem.