A user says that the video on their desktop computer is not correctly displaying. There are various points on the screen where the screen does not light up; these are always black dots. This is a sign of _______.

Dead pixels are areas of the screen that never light. You may look for these by changing the background to white and observing if any spots don't light up. If the display is still under warranty, you should return it, but there isn't much you can do to fix a dead pixel.