What causes the condition "webbed feet" & "webbed toes"?

Webbing of toes. Incomplete separation and differentiation of the toes during gestation is the cause. It can be corrected surgically if indicated.
No one REALLY knows! Webbed toes is the common name for syndactyly affecting the feet. It is characterised by the fusion of two or more digits of the feet. In humans it is considered unusual, occurring in approximately one in 2, 000 to 2, 500 live births. The exact cause of the condition is unknown. The toes can be surgically seperated, but there is no real reason to do this.