It's = it is or it has or it *s
Its = belonging to it

Yes, yes, I get it. Apostrophes usually denote possession.

Emily's car

But the word "it" is an exception. It just is. Get used to it.

The gridview keeps losing its values.
11PM is when you can see the sky at its best.
You don't realize that it's my car that you're siphoning from.
It's really difficult to understand the difference between it's and its.

Write this rule down and put it in a place that is always visible to you, such as the insides of your eyeballs.