LCD screens are the most likely component to contain noticeable flaws in the form of the dreaded dead pixels. There are 3.9 million sub-pixels (red, green and blue) on a standard 1280×1024 resolution LCD monitor, and each of these is a transistor. Occasionally these individual transistors responsible for carrying current to a pixel will either short out or remain open resulting in what is called a dead pixel. Dead pixels are rare and largely go unnoticed by the user.
A “lit” pixel is one that appears as one of several randomly placed white, red, blue or green pixel elements on a dark background, or you may have a “missing” pixel which shows up as a black dot on a light colored background. Apple prefers to call it “pixel anomaly”.
To download the tool and read more about it, go to Digital Inspiration
Update : Feel free to download Rizone’s Pixel Repair