Move Cursor While Paging Through Files
Here's a quick Friday tip for those who like to navigate open documents via the keyboard. In many OS X applications, including TextEdit, pressing Page Up and Page Down don't actually move your cursor position within a document. Instead, they move only the view. So if you click on the first line of a TextEdit file, then press Page Down three times, and then type something, the window will jump back to the first line, and that's where your typing will appear.
To move the cursor position with the view point, press and hold Option before pressing Page Up or Page Down. This will move the cursor into the line in the middle of each screen as the display moves up or down a screenful at a time. Now when you start typing, the typing will appear on that center line of the current screen, instead of on the last line you happened to click.
This trick does not work in every application, though, so you'll have to experiment to find those where it does.