What goes up but never goes down?

Answer for the previous riddle: holes
The next question is in the video below.

You can get the answer if you click the link inside the video.

Next riddle: What goes up but never goes down?
 
My videos can be found on YouTube. The riddles are inside my videos. I upload videos with this username: IhaveBIGplan
Play free online games or make money from your flash games - link
Site created with: link | link 2