Dark spot on LED screen - WTF?!

My dad's ThinkPad L412 has got a small dark spot on its screen. It's not completely black, it's a grey irregular shaped (almost circular) spot. I thought it was a dirt particle so I tried cleaning but that didn't help. The spot's diameter is hardly half millimeter and is hardly noticeable except if there is a solid color displayed in that area. I have confirmed it is NOT a stuck pixel because a stuck pixel shows varying colors depending upon the color displayed. If it is a dead pixel, it must be black. But it is not. It is very very light grey in color and appears the same no matter whatever is displayed. I tried many dead pixel apps but none helped. Can you help me sorting out what exactly that spot is?

nilanko said:
If it is a dead pixel, it must be black. But it is not. It is very very light grey in color and appears the same no matter whatever is displayed

A quick google search revealed that dead pixels can be of different colors (but I'm not that sure)

See:
dead pixel color ?
Grey DOT on LCD screen???

It might be a dead pixel.

But it's larger than a pixel and a dead pixel is generally sharp but mine is blurry -- about half a milimeter.

I used a magnifying glass to see that area of the screen. I could clearly see small squares. None of the light squares were off. Only 2 squares were less lit (white display in that area) which is making a 'grey spot' or dull spot. It is neither a dead or stuck pixel cause it's only less lit. What might be that?

I once sat on my laptop
it developed a huge black spot in the center of the screen.
I took it for repair and told the guy at the shop exactly what happened.
What did he do?
he took a piece of paper
made a paper ball from it
rubbed it on the flat surface of a table to get a flat surface on the paper ball
next he rubbed the same on the screen gently(but with a little bit of pressure) with the screen off
after that he turned the screen ON and the spot was gone.
It was like magic!

thats a new technique.....

@noja: will try that.

I tried the UDPixel app and also the message technique, all this made the spot fainter but it didn't go away, also its shape has changed a bit.

whats udpixel app??

^^Helps in correcting stuck pixels. But my case is neither stuck or dead.

noja said:
I once sat on my laptop
it developed a huge black spot in the center of the screen.
I took it for repair and told the guy at the shop exactly what happened.
What did he do?
he took a piece of paper
made a paper ball from it
rubbed it on the flat surface of a table to get a flat surface on the paper ball
next he rubbed the same on the screen gently(but with a little bit of pressure) with the screen off
after that he turned the screen ON and the spot was gone.
It was like magic!

That wasn't magic. Dead pixels can't be removed like that. Your screen just had some sticky dirt on it which is why he was able to remove it.