水平居中
.div {
margin: 0 auto;
width:500px ;
height:300px;
border: 1px solid red;
}
水平垂直居中
方式一:
.div {
width: 500px ;
height: 300px;
margin: 150px 0 0 -250px;
position: relative;
left: 50%;
top: 50%;
border: 1px solid red;
}
方式二:
.div {
width: 500px ;
height: 300px;
margin: -150px 0 0 -250px;
position: absolute;
left: 50%;
top: 50%;
border: 1px solid red;
}