Today, I've cleaned my laptop screen and noticed white spot that can be seen behind a white background pixels. There are about 3 or 4 of these little spot on the right and left side of screen. It seems like they are formed when something had hit with screen. Any idea what can they be, if they are permanent?
Well... with LCD, white isn't so much a color as it is the absence of any filtering in the liquid crystal, allowing just the white background to reflect light through. That said, you can see the white spots behind white background pixels. What happens when there is a color over that spot. Do you still see some kind of mark there? Are you sure it is not something on the screen (sneeze debris, etc) that didn't come off when you cleaned it?
If they stay white regardless of the color there, but only show when the screen is on, then they are most likely now dead pixels.
But it is really hard to mark up the background reflector that is behind the LCD panel.