Quote Originally Posted by sapi
@Husar and others: you can check for a dead pixel, rather than dirt, using a tool such as this

Run the time cycle, and carefully check the screen for any place where it is not an absolutely uniform colour.
I actually emulated such a program myself in Corel Photopaint, by showing a unicolour picture in full screen mode. And some of my dead pixels are only dead concerning a certain colour, with other colours they work fine, but you don't notice it except if you look closely and know what to look for in this case. I usually forget about it completely until a topic like this one comes up.
Oh, and I already noticed that dirt can make it look like there's a dead pixel, always check for dirt before returning the thing.

Alsonote that there are pixel error classes and most monitors are class two, which means no guarantee unless a certain number of pixels are dead or false(there is more than a dead pixel, can also be a dead subpixel etc), only class 1 allows no dead pixels, but it can be hard to find an affordable monitor rated class 1, IIRC Phillips has some oh and here is a list of others.