Keyboard Scrolling in Lion Application Windows
Although you can set scrollbars to always display in windows, there is no option to show the actual scrollbar arrows anymore in Mac OS X Lion. A simple workaround to get used to this is to start using the keyboards up and down arrow keys instead.
(via: OS X Daily)
Also note that while you hold down the Option key and type the up or down arrow you’re able to scroll by an entire page as it’s displayed on screen. And when you add the Command key to the mix you’re able scroll all the way to the top or bottom of a page.
I’m pretty sure this method of scrolling has worked in earlier versions of OS X — at least 10.6 that I’m sure of, and probably all the way back to 10.3, if not before that.
Still, it’s a handy trick to learn if you like to navigate using the keyboard.