.cassdong{
	width: 353px;
	float: left;
	margin-right: 70px;
	margin-bottom: 30px;
}
.cassdong:nth-child(3n){
	margin-right: 0px;
}
.cassdong a img{
	width: 353px;
}
@media  (max-width:767px) {
	.cassdong{
		width: 100%;
	}
	.cassdong a  img{
		width:100%;
		max-width:100%;
		height:auto;
	}
}