Pterygium colli deformity (well what I meant was - Webbed Neck!)

Congenital skin fold that runs along the sides of the neck down to the shoulders. 

This is seen in Turner syndrome and Noonan syndrome, and  Klippel-Feil syndrome

In the newborn period, webbed neck is the loose folds of skin on the neck. 
As the child grows, the skin may stretch out to look like there is either a very short neck or no neck at all.

A 12-year-old female with Noonan syndrome exhibiting a typical webbed neck.
Picture courtesy: Wiki commons

Cystic Hygroma

A cystic hygroma is a congenital multiloculated lymphatic lesion that can arise anywhere, but is classically found in the left posterior triangle of the neck.his is the most common form of lymphangioma
Cystic hygromas occur in approximately 1% of fetuses between weeks 9 and 16 of pregnancy
Cystic hygromas can occur as an isolated finding or in association with other birth defect. Because the risk for a chromosome abnormality approaches 50% when a cystic hygroma is found prenatally, amniocentesis or CVS (chorionic villus sampling) can be performed to diagnose these conditions.Cystic hygromas that develop in the third trimester (after thirty weeks gestation) or in the postnatal period are usually not associated with chromosome abnormalities. There is a chance of recurrence after surgical removal of the cystic hygroma.
A common association is Turner Syndrome. Severe form of this is HYDROPS.

Image Courtesy: DermAtlas

Video: Youtube