Its / It's

One of the most common mistakes I see on blogs and elsewhere is the use of it's when the word should be its. It's should be used only when meant as a contraction of the phrase it is. To make it as simple as possible -- my goal here, after all -- if you can replace the word with it is, then use it's. Very often, writers think the apostrophe shows possession, like it does nearly everywhere else, but this is one of the few cases where that's not correct.

Some examples:

It's raining cats and dogs -- it is raining cats and dogs, so it's is correct. Well, the usage is correct, but the sentence is so far off here in northern Minnesota that I'm almost ashamed to use this example. It's (it is!) a balmy 21 degrees and snowing.

The dog chased it's tail -- the dog did not chase it is tail, so use its.

...in all its glory -- in all it is glory? Please, use its.