Clean riddles with simple answers

What comes down but never goes up?

I always come down and never ever go up? Think, think and think! We all just love it.

I know a word which reads the same when written forward, backward or upside down. Do you?

You write on me and secrets I can keep. In places never seen. I spin like a top. Though stiff as a board, I'm often described like a mop. What am I?