*{margin:0;padding:0;list-style: none;border:0;}
.poster-main{ position:relative; width:800px; height:420px; }
.poster-main a,.poster-main img{display:block;}
.poster-main .poster-list{width:800px;height:270px;}
.poster-main .poster-list .poster-item{ position:absolute;left:0;top:0;}
.poster-main .poster-btn{ position:absolute;top:0;width:100px;height:270px; z-index:10; cursor:pointer;  opacity:0.8}
.poster-main .poster-prev-btn{left:0; background: url(btn_l.png) no-repeat center center;}
.poster-main .poster-next-btn{right:0; background: url(btn_r.png) no-repeat center center;}