.fold_wrap{
    width:100%;
    height:100%;
    overflow:hidden;}
.fold_wrap li{
    float:left;
    width:20%;
    height:100%;
    position:relative;
    overflow:hidden;
    cursor:pointer;}
.fold_wrap li .mask_b{
    position:absolute;
    overflow:hidden;
    width:100%;
    height:100%;
    right:0;
    bottom: 0;
    text-align:right;}
.fold_wrap li.active .mask_b{
    background:none;}
.fold_wrap li .mask_b h4{
    color:#fff;
    width:100%;
    margin:0 auto;
    display:block;
    position:relative;
    right:40px;
    padding-top:30px;}
.fold_wrap li.big{
    width:875px;}
.i_how_n1{
    top:370px;}
.pic_auto{
    width:100%;
    height:100%;}