I received this mail and it was something like illusion and playing with mind and Limitation of our Eye.
Have a look at this Image !!!
If your eyes follow the movement of the rotating PINK DOT, the dots will remain only one color, PINK.
However if you stare at the black ‘ +‘ in the center, the moving dot turns to green.
Now, concentrate on the black ‘ + ‘ in the center of the picture. After a short period, all the pink dots will slowly disappear, and you will only see only a single green dot rotating.