【CSS】定位元素居中显示

p {
    width: 100px;
    height: 100px;
    background-color: skyblue;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -50px;
    margin-left: -50px;}

p {
    width: 100px;
    height: 100px;
    background-color: skyblue;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);}

p {
    width: 100px;
    height: 100px;
    background-color: skyblue;
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right : 0;
    margin: auto;}