Absolutely positioned box centered

Today I learned a very practical css as follows:

div{
    width: 600px;
    height: 60px;
    background: #13ce66;
    position: absolute;
    left: 50%;
    top: 0;
    margin-left: -300px;  /*组件真实宽度的一半 这里是600的一半*/
}

Recorded as a formula, it is left: 50%; margin-left: half of the negative width.