#about .col-left .img{
width: 100%;
height: 100%;
position: relative;
border: 10px solid black;
z-index: 0;
}
#about .col-left .img::after{
content: "";
position: absolute;
left: -33px;
top: 19px;
height: 98%;
width: 98%;
border: 7px solid yellow;
z-index: -1;
}
如何使白色边框在他们的交汇点显示在黄色边框上方?
