"TFT screens have thousands of pixels, on a 1024x768 monitor, there are three cells for each pixel - one each for red, green, and blue - which amounts to nearly 2.4 million cells (1024x768x 3 = 2,359,296). There's only a slim chance that all of these will be perfect; more likely, some will be stuck on (creating a "bright" defect) or off (resulting in a "dark" defect). DPT was written to help me check my own screens by cycling through the three primary colours used (red,green,blue) and all on (white) and all off (black). Simply select a colour then closely inspect your monitor in each of the primary colours checking for pixels that are not operating as expected. Stuck pixels (always on) are easier to noticed then pixels that are not on due to their size (normally under .5mm). "
http://www.dps.uk.com/freeware_DTP.htm
regshot tested.