Doing predictions based on the color of nails (white or black) in Hindu religion is part of Samudrika Shastra. It is believed that the different color of nails indicates what is going to happen in future. It is believed that nails reveal the habits and character of a person. It is also used for early prediction of diseases.
If there is a crescent white mark (half moon) on any nail then it suggests auspiciousness and better luck. The person will hear happy news.
Too many white marks on nails indicate problems related to marriage – delay in marriage (sudden decision to stop marriage etc). There will be problems in married life too. It also means that person has the habit of lying.
If there is a prominent white mark on index fingernail (the finger near thumb), then the person will find new friends or get into a relationship. It also indicates success and achievement.
White mark on middle fingernail suggests that you are having an enemy among friends or relatives. You might be unable to identify as to who is your friend or enemy.
White mark on ring finger nail suggests good luck. It will bring a change of fortune.
White mark on little fingernail indicates journey. It might be career related or like a vacation. There will be success and happiness because of the travel.
White mark on thumbnail indicates desire fulfillment or you will get some materialistic thing that you had longed for.
Black mark or line on any nail indicates bad luck. There will be unexpected problems in life or accidents. Such people should be careful in money matters. They should avoid unwanted talks and fights with people. They might be involved in scandals or will be hit by gossip or character assassination.