html---阴影效果

html：
<div class="ad">
			<div class="ad_block">
				<div class="ad_block_item item1">
					
				</div>
				<div class="ad_block_item item2">
					
				</div>
				<div class="ad_block_item item3">
					
				</div>
				
			</div>``

css:
/*=============ad css start======================*/
.ad{
	float: left;
	/*position: absolute;*/
	background:#F8F8FF;
	width: 100%;
	height: 400px;
	/*margin-top:60%;*/
}
.ad_block{
	width: 85%;
	background: #F8F8FF;
	height: 100%;
	margin-left: auto;
	margin-right: auto;
	
}
.ad_block_item{
	position: relative;/*绝对定位*/
	top: 0px;
	width: 29%;
	height: 90%;
	background: #FFFFFF;
	border: 1px solid #000000;
	float: left;
	margin-left: 40px;
	/*margin-right: 40px;*/
	margin-top: 35px;
	border-radius: 5px;
	transition: all 0.5s ease-in-out;
	
}
.ad_block_item:hover{
	box-shadow: 0px 1px 25px 5px #808080;
	top: -8px;
}
.item1{
	border-top: 3px solid red;
}
.item2{
	border-top: 3px solid green;
}
.item3{
	border-top: 3px solid blue;
}
/*=============ad css end======================*/