/* div在屏幕中居中對(duì)齊的方法一：*/
margin: auto;
position: absolute;
top: 0;
left: 0;
right: 0;
bottom: 0;
/* div在屏幕中居中對(duì)齊的方法二：*/
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%,-50%);
/* div在屏幕中居中對(duì)齊的方法三：*/
display: flex;
justify-content: center;
align-items: center;
