Each pixel in an LCD has three transistors. One for the color red, green, and blue. This application will test these transistors in all relevant states.
LCDtest can only help you identify back or stuck pixels on your LCD. It cannot repair the monitor. Once you have identified a pixel that is not working properly you may be able to fix the issue with a massaging technique that is explained in the application.
LCDtest is a free utility and does not cost anything to download or use.