What is the third value in CSS padding?

Question

I am playing around with the Less Framework 3 and I saw this line in the css:

body {     padding: 60px 42px 0;     width: 396px; } 

what does padding: 0 do?

This does not look like normal css shorthand, and top-right-bottom seems weird.

Answer 1

The padding and margin properties specify top right bottom left.
If left is omitted, it will default to right.

Thus, padding: a b c is equivalent to padding: a b c b.

If bottom is also omitted, it will default to top.
Thus, padding: a b is equivalent to padding: a b a b.

If right is also omitted, the single value is used for all 4 sides.
Thus, padding: a is equivalent to padding: a a a a.

Answer 2

When you specify three values the second is implicitly used for the fourth, i.e. padding: 60px 42px 0 42px;