.slider_wrap {
	margin:100px auto 0;
	width:640px;
	height:400px;
	position:relative;
	overflow:hidden;
}
.slider_wrap img {
	width:100%;
	height:auto;
	display:none;
	position:absolute;
	top:0;
	left:0;	
}
.slider_wrap img:first-child {
	display:block;
}