One of the major changes in OS X 10.7 Lion is the way scrolling works. Apple changed it to mimic the way you scroll in iOS. Up is down and down is up? It takes some getting used to. Luckily, you don't have to. Here's how to make your mouse or Trackpad scroll the way it used to -- when up meant up and down meant down.
First, if you're using a mouse, open System Preferences. Click on the Mouse icon.
On the next screen, uncheck the box next to Move Content in the Direction of Finger Movement when Scrolling or Navigating.
Close out of System Preference. Your mouse will now scroll the way it always has before the Lion release. This is handy if you use a PC mouse with your Mac, too.
If you're using the Trackpad on your MacBook or Apple's external Magic Trackpad to navigate Lion, open System Preferences. Click on the Trackpad icon.
Then click on the Scroll & Zoom tab. Uncheck Scroll Direction: Natural.
Now scrolling will work the same way it did before you upgraded to OS X 10. 7 Lion.
Some people really like the new scrolling and navigation in OS X Lion. It matches the way they're used to working their iOS devices. But you don't have to go along with that.