题解 | #浮动和清除浮动#

.wrap::after{
                /*补全代码*/
                content:"";
                display:block;
                clear:both;
            }
             .left {
                width: 100px;
                height: 100px;
                /*补全代码*/
                float:left;
                
            }
             .right {
                width: 100px;
                height: 100px;
                /*补全代码*/
                float:left;
            }