My 50" plasma has pixcel dust that comes and goes. what is pixcel dust and how do i fix this?

This is called diffusion and a lot a plasma tvs get this. It usually is a to high/to low voltage setting inside the unit and needs to be adjusted. This should be done at a repair shop because the voltage needs to be watched with a volt meter as adjustments are made. Different makers have different settings and names on thier voltages. These are very high and dangerous voltages and if the wrong ones are turned the unit can be badly damaged. What may be an easy fix can be turned into having to buy a new set.