On the Mac if you need to scroll horizontally and you don't have a Mighty Mouse (which has horizontal scroll built-in), there are still easy ways to scroll horizontally. If you are using a Macbook or Macbook Pro, you can put two fingers on the scroll pad, and move your fingers left and right to scroll horizontally. Your fingers go on the trackpad in the "normal" scroll position, side-by-side, same as if you were going to scroll vertically. If you have a mouse with a scroll wheel, you can hold down the shift key. When the shift key is held down, the scroll wheel on your mouse will scroll left and right instead of going up and down.