Anatomy of dead pixels
Faulty pixels appear as black or colored dots on an all-white background. In addition, some pixels can stay in a permanently "turned-on" state (this is more common than dead pixels), resulting in a white, red, green, or blue pixel on an all-black background.

There are 3.9 million sub-pixels (red, green and blue) on a standard 1280x1024 LCD monitor, each of these is a microscopic transistor. While the defective rate of pixels on LCD monitors and TVs is very low, due to the large number of sub-pixels, manufacturers cannot guarantee 100% error-free panels at an affordable price. To make things more difficult, it is not possible to test any pixels before full assembly of the panel, and fixing any pixels is not possible after assembly.

How can you avoid them?
It is a good practice to check the LCD monitor or plasma TV with Dead Pixel Locator before purchasing, although not all vendors allow it. Still, every manufacturer has a dead pixel policy, which you should read carefully. If you find any defective pixels on your new LCD monitor or TV during the warranty period, it may qualify for a replacement!

The application displays homogeneous colors on the monitor. Use the arrow keys to change the colors, and check every part of the screen very carefully for every color. If you find any pixels that have different colors than the background, first make sure that it is not the dust on the surface of the screen. :-) If you cannot wipe it off, that is a defective pixel.