On displays such as LCD and CRT, these are defective pixels that either will not illuminate, emit an incorrect color, or (on LCD displays) are ‚Äústuck‚ÄĚ illuminated. They are an accepted defect of the manufacturing process, where X percent (varies with manufacturer) of pixels must be
non-functional before the entire display is considered unusable. Stuck illuminated out pixels on an LCD display can be very annoying as they are easily noticed. If you do not want these defects on your laptop's screen, buy from a dealer that has a good return policy which will allow you to exchange laptops until you get one with a flawless display.