Have you ever restarted your computer and found that your display changed its resolution, making all the icons and menus smaller than before?
If you're using Mac OS X, 800 x 600 is the minimum recommended resolution for most displays. However, sometimes you may see that other resolutions, such as 600 x 400 or 800 x 500, are available when you're running Classic, playing certain games, or using some multimedia applications. If you set your display to use one of these resolutions, the computer will default back to the minimum 800 x 600 when you restart it.