Div水平垂直居中的几个方法

方式一：

.parent {
    width:500px;
    height:500px;
    border:2px solid red;
    position:relative;
}
.child {
    width:200px;
    height:200px;
    margin: auto;  
    position: absolute;  
    top: 0; left: 0; bottom: 0; right: 0; 
    background-color: red;
}

方式二：

.parent {
    width:500px;
    height:500px;
    border:2px solid red;
    position:relative;
}
.child {
    width:200px;
    height:200px;
    margin:auto;
    position:absolute;
    left:50%;
    top:50%;
    margin-left: -100px;/*使用负值margin将子块偏移自身宽度值的50%*/
    margin-top:-100px;
    background-color: red;
}

方式三：

.parent {
    width:500px;
    height:500px;
    border:2px solid red;
    display:table-cell;
    vertical-align:middle;
    text-align: center;
}
.child {
    width:200px;
    height:200px;
    display:inline-block;
    background-color: red;
}

方式四：

.parent {
    width:500px;
    height:500px;
    border:2px solid red;
    display:flex;
    justify-content:center;
    align-items:center;
}
.child {
    width:200px;
    height:200px;
    background-color: red;
}