It's often difficult to see
The much abused apostrophe.
Its key is way off to the side
Sometimes it's NOT there for its ride.

Possessive? Plural? Get it right!
Contraction's simple day or night.
It is is it's and its belongs
To someone, somewhere for a song.

A careless writer must do more
To improve her language score.
There's no excuse for such a twist
It's simple to see where it fits.

Blame the keyboard for its speed
Quill and ink made slower reads.
'No excuse! ' again, I said..........
One more time my face is red.

Herbert Nehrlich

http://www.poemhunter.com/poem/its-and-it-s-an-iq-test-by-rachel-my-kindred-spirit/