Instead of specifying an element'smargin-top, margin-right, margin-bottom, and margin-left attributes, you can specify them all in one line, like this: margin: 10px 20px 10px 20px;.
These four values work like a clock: top, right, bottom, left, and will produce the exact same result as using the side-specific margin instructions.
.green-box {
background-color: green;
margin: 40px 20px 20px 40px;
}