OS X 10.7 Lion has reversed the typical scroll direction used. Thankfully, changing this is an easy fix!
Note: Mouse (if plugged in) and Trackpad have separate settings for scrolling!
1. Locate the Mouse and / or Trackpad options in System Preferences.
2. In the Mouse option uncheck ‘Move content in the direction of finger movement when scrolling or navigating’.
3. In the Trackpad option uncheck as shown below:
Newer Macs look like the image below. Under Scroll and Zoom, uncheck ‘Scroll direction: natural’.
Older Macs look like the image below. Uncheck ‘When using gestures to scroll or navigate, move content in the direction of finger movement.’