http://www.mayoclinic.com/health/nail-fungus/DS00084/METHOD=print
Mayo Foundation for Medical Education and Research
Nail fungus is a fungal infection in one or more of your nails. An infection with nail fungus may begin as a white or yellow spot under the tip of your fingernail or toenail. Learn about the causes, symptoms, risk factors,diagosis, treatment and prevention of nail fungus.