属性选择:

操作的模块
position:
top:
px
left:
px
bottom:
px
right:
px
z-index:
opacity:

code:

box_A:
box_B:
box_C:
box_D:
box_E:
box_F:

效果:

外层虚线有个position:relative;属性

box_A
box_B
box_C
box_D
box_E
box_F