Babies normally are born with two soft spots (fontanelles) on their head: a large soft spot on the top and a small one on the back. The soft spots are areas where the bones of the skull have not yet grown together.
Although they are called soft spots, these areas are made of tough fiber and can be touched gently.
When a soft spot becomes hard, it is considered closed. By age 4 months, the soft spot on the back of the head has closed. By age 2 years, the soft spot on the top of the head has closed.
Bulging of a fontanelle (soft spot) is a sign of increased pressure inside the skull.
WebMD Medical Reference from Healthwise