.poster-main {
    position: relative;
    margin:0 auto;
    width: 900px;
    height: 400px
}
.poster-main a, .poster-main a img { display: block; }
.poster-main .poster-list {
    width: 900px;
    height: 400px
}
.poster-main .poster-list .poster-item {
    position: absolute;
    left: 0;
    top: 0;
    border:10px solid #fff;
    box-shadow: 0 0 30px rgba(0,0,0,.8);
}
.poster-main .poster-btn {
    position: absolute;
    height: 100%;
    width: 100px;
    top: 0;
    z-index: 10;
    opacity: 0.9;
}
.poster-main .poster-prev-btn {
    left: 0;
    background: url("../img/btn_left.png") no-repeat left center;

}

.poster-main .poster-next-btn {
    right: -20px;
    background: url("../img/btn_right.png") no-repeat right center;

}