Most computer programs paint images in the screen. Some of these images (letters, pictures, animations, menus) are usually moving or changing, and never stay in the same place for long. But some portions of the screen are always in the same place, sometimes for hours or even days or months.
These sorts of images, continuously drawn in the same place for a long time, could damage the screen because the electron rays always hit the same points on the screen. Damage would consist in poor image quality, and th......