Information regarding the Nintendo DS Lite LCD Screens
Extremely high precision technology is employed to produce the Nintendo DS Lite LCD screens. The result is more than 99.99% effective pixels with a mere 0.01% of the pixels inactive or always lit. You will find this situation in many LCD devices (PC monitors, televisions, cell phones, etc.). However, this is not a malfunction.
It is important to understand that this issue will remain limited to the pixels you have already noticed. The problem will not get any worse and you should not expect to see the problem in any other areas of the screen.