.img {
position:relative; 
background:#999; 
margin:10px;
}
.img span {
display:block;
border:0px solid #333;
background:#FFF;
position:relative;
padding: 0px;
}
.right {/*阴影在右边时*/
top:-5px; 
left:-3px;
}
.left {/*阴影在左边时*/ 
top:-4px; 
right:-4px;
}