Take a good look at your notebook computer screen. Do you find some tiny dark spots? You could have dead pixels. One of most expensive parts of your notebook computer is LCD screen.
LCD's are highly sensitive and any amount of pressure, touching or handling may damage it. As such, dead pixels aren't an uncommon thing. Apparently, some degree of dead pixels is to be expected. Still if you have a lot of them, it would be classified as a defective screen. So, how do you determine if you have dead pixels?
Before we go there, make sure it's not just dust. Clean your screen first. The best way to do that is to use a soft cotton cloth - no rags or paper towel as they can scratch your screen easily. Moisten cloth with plain old water and wipe screen gently.
Side note: I've also tried maintaining my screen dust free with a Swiffer Duster. These are inexpensive, very soft and they pick up dirt not just re-distribute it. It has worked well. Of course, this will not take care of smudges or dried on dirt. So you'll still have to use cotton cloth and water combo sometimes.
Once you've cleaned it, you can run a quick check with a free software called Dead Pixel Buddy. It's basically a very simple file that will rotate your screen through all basic colors. This way you can tell if a pixel on your screen is not displaying properly. One tip, you might want to get a help of a friend. Two sets of eyes are better than one especially since pixels tend to be miniscule.