VIP26/day17/css/1.盒子水平垂直居中.css

* {
    margin: 0;
    padding: 0;
}
html,body {
    height: 100%;
}
#box {
    width: 400px;
    height: 400px;
    background: #f00;
    position: absolute;
    top: 50%;
    left: 50%;
    /* 减去自身宽高的一半 */
    margin-left: -200px;
    margin-top: -200px;
}