OS X Lion introduced a new way of scrolling, but it is completely opposite of the typical type of scrolling that most people are used to. However, this can be extremely frustrating to people switching to Mac or simply upgrading from Snow Leopard to Lion. Now, if you use the scrolling for a few days, you should be able to adjust to it over time. However, for people who can't adjust or often switch between their Lion Mac to a Snow Leopard/Windows/Linux machine, Apple has included a way to return the scrolling to its pre-Lion state.
Step 1: Open System Preferences
You'll find System Preferences either as a series of gears on your Dock by default, but if you removed it, you can find System Preferences either in your Launchpad or your Applications folder.
Step 2: Tweak the Scroll Direction
After launching System Preferences, click on the Mouse panes under Hardware. If you are using a trackpad, don't worry. This process will still return scrolling to normal on a trackpad as well. In Mouse preferences, uncheck "Move content in the direction of finger movement when scrolling or navigating" at the top of the preference pane.
And that's it. Your scrolling on your Mac is now back to normal – or at least normal by the standards of most of the world.