There Is No "CSS leading" Property
The CSS line-height property is similar to leading in desktop publishing — it determines the "line height". Leading gives the impression of lines of text being closer together or further apart.
The CSS specification uses the line-height property to apply leading. Half of the line-height is taken as the upper leading, and half of the line-height is taken as the lower leading.
Default for line-height
The default for line-height is normal. This is typically between 1.0 and 1.2.