2018-11-22清除浮动

clear
.box{
    width:100px;
    height:100px;
    background-color:red;
    clear:left;
}
清除左浮动
.box{
    width:100px;
    height:100px;
    background-color:red;
    clear:right;
}
清除右浮动
both 可以清除对它影响最大的浮动
可以解决高度塌陷
.clearfix:after
.clearfix:after{
    content:' ';
    display:hidden;
    clear:both;
}
谁塌陷就加上clearfix