让div水平垂直居中

方法一、用绝对定位让div水平垂直居中

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

方法二、通过flex布局让div水平垂直居中

div的父级 {  //在div的父级设置
            display: flex;
            align-items: center;
            justify-content: center;
            background-color: red;
            width: 100px;
            height: 100px;
        }

方法三、用绝对定位+margin负间距

div {
            position: absolute;
            left: 50%;
            top: 50%;
            margin: -100px 0 0 -100px;
            background-color: red;
            width: 200px;
            height: 200px;
        }

方法四、用绝对定位+translate平移

div {
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
            background-color: red;
            width: 200px;
            height: 200px;
        }

方法五、通过设置父级为table-cell实现div垂直水平居中

div的父级 {
            display: table-cell;
            vertical-align: middle;
            text-align: center;
            background-color: red;
            width: 100px;
            height: 100px;
        }