How to check iMac LCD

Try a fullscreen of a movie, but pause it before anything comes up (you need one that fades in), you should have a black screen. Check for stuck pixels. Press command + option + control + 8 to invert the screen to total white, then check again and invert back to normal with the same shortcut. If you find any stuck pixels, you can use this free iPhone (it will work for your iMac too though, click on "repair iPhone LCD") stuck pixel fixer, just leave it flashing over the pixel for an hour or so and see if it can be fixed. If not, you should be able to live with a stuck/dead pixel or two.

 

B + W

A full black screen and a full white screen should show you pixels that don't change colour.

The white is just in case a pixel is fixed on black.


Edit: Eggs after easter I see

 

Pixel Check is the best program I know of for checking for stuck/dead pixels.