css 弹框浏览器居中

.father {　  width: 300px; height:150px;　  position: relative;}.son { 　  position: absolute; 　  top: 0; right: 0; bottom: 0; left: 0;

 

 或

.class{ position: absolute; width: 100px; height: 100px; margin: auto; top: 0; right: 0; bottom: 0; left: 0; background: red; }