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 1280x1024 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".
Dead Pixel Locator is a neat utiltiy to check the LCD monitor or plasma display for dead pixels. It checks the LCD screen for dead pixels and displays the faulty pixels in a color different than the background color.
How to fix dead pixels ? Fixing dead pixels may involve a bit of luck. If you notice dead pixels, try rubbing the LCD screen area gently by pressing a finger gently through a rag around the pixel.
Remember that notebook manufacturer have their own policy on how many dead pixels warrants a return and replacement. Dell considers a screen defective only if it has six or more faulty pixels. The problem is, most people are not aware of this policy before they get their notebook and falsely assume that one dead pixel is good enough to ask for a replacement, but this is generally not the case.