I can never remember this - so am noting it here
Four padding values can be declared at once by either specifying two or four values. When only using two values, the first will define the padding on the top and bottom, while the second will define the padding on the left and right.
When using the four value padding specification, the corresponding directions are: top, right, bottom, left. To help you remember what the order is, just remember that it starts at the top and then moves clockwise until it reaches the left. The examples below shows partial (2) and complete (4) padding usage.
padding: 5px 15px;
border: 1px solid black;
padding: 0px 5px 10px 3px;
border: 1px solid red;