I bought a used 24 inch cinema display a few weeks ago. I just noticed maybe two dead pixels (adjacent to each other) on the left side of the screen last night. I first thought it is just dust so I wipe off the screen. But it is still there. I open the glass cover and clean the inside of the glass as well as the surface of the LED panel. The dead pixel is still there. It disappear in black screen but is visible in all other colors. It is hard to say what color it is but it appears that it changes color when you look at different angle. Also, it seems the pixel moves when you look at it from different angles. I put the mouse pointer right under the pixel. Then if I move my head right to left, I can see the pixel move location compared to the pointer. This is rather confusing to me. Is it really a dead pixel or is it dirt somewhere? Thank you for your help!