By default the Mac OS X Lion Operating System reverses the standard mouse wheel scrolling direction. This change was made with the release of the Mac OS X Lion Version 10.7, to allow a more natural mouse scrolling method (similar to push scrolling or scrolling in the same direction as you would when finger scrolling touch screens).
Some folks feel this is awkward and backwards and prefer the original mouse scrolling methods where down scrolls down and up scrolls up the page.
The good news is that the Mouse Scrolling Direction can easily be changed back to how it was in Mac OS X Snow Leopard and prior versions by simply un-checking a mouse option.
Reverse Mouse Scrolling Direction on Mac OS X Lion
(1.) Navigate to System Preferences (2.) Under Hardware, Select Mouse
Uncheck the option to "Move content in the direction of finger movement when scrolling or navigating".
Close the window, and enjoy your Old School Scrolling method!