.slideshow{
	width:250px;
	height:200px;

	float:left;
	position:relative;
}
/* img要素は絶対配置で一か所に重ねる */
.slideshow img{
	position:absolute;
	top:0;
	left:0;
	border:0px solid #000;
}
/* 2番目以降のimg要素にclass="alt"を付け、消す */
.slideshow img.alt{
	display:none;
}