Certain lines and spots on nails have following effects :
Vertical lines on nails are symptoms of muscular problem. If there are white spots like half-moon or full-moon, then it is a sign of defect in blood circulation.
Several red spots on nails indicates that the person is of wicked nature.
Black, bright dots on thumbnail indicates that the person is full of lust and criminal minded.
Generally, black spots on nails indicates anxiety, fear, sadness; white spots indicates happiness in life; blue spots indicates bad luck and yellow spots indicates death.
If a white spot remains stable at some place on nail, then it indicates stature and love for kinsfolk.
If there are several white spots on nails, it indicates faulty digestive system.