box1和box2 margin叠加
box1
box2
box1和box2 margin叠加
box1和box2 margin不叠加--box1创建BFC
box1和box2 margin不叠加--box1具有padding或border
box1和box2 margin不叠加--box1具有padding或border
box1和box2 margin不叠加--box1或box2 display:inline-block
box1和box2 margin不叠加--box1或box2具有float属性