Good Riddles

Question: A man walks into a completely dark room. There is a box on a table at the other end of the room and immediately the man knows one of the contents of the box. He cannot smell, see, or hear it.

How does he immediately know what is inside?

Question: Why don't most buildings have a 13th floor?

Question: I wear a red coat and have a stone in my throat.

What am I?

Question: What's always coming, but never arrives?

Question: I'm heavy but not backwards.

What am I?