.banner{
    width: 100%;
    height: auto;
}
.banner img{
    width: 100%;
}
.ab-top {
    width: 100%;
    height: auto;
    display: inline-block;
    border-bottom: 1px solid #e8e8e8;
}
.abt-left {
    float: left;
    line-height: 65px;
    letter-spacing: 1px;
}
.abt-left img {
    float: left;
    margin-right: 6px;
    margin-top: 24px;
}
.abt-left p {
    float: left;
}
.abt-left p a {
    color: #434343;
}
.abt-nav {
    float: right;
    line-height: 73px;
}
.abt-nav li {
    float: left;
    margin-left: 45px;
}
.abt-nav li:hover{
    border-bottom:1px solid#1e63ac;
}
.abt-nav li a {
    color: #000;
    font-size: 18px;
}
.case-box{
    width: 100%;
    height: auto;
    margin-top: 20px;
    display: inline-block;
}
.case-box li{
    float: left;
    width: 24%;
    margin-left: 6px;
    margin-right: 7px;
    margin-bottom: 12px;
    position: relative;
}
.span{
    position: absolute;
    top: 0px;
    width: 100%;
    height: 97px;
    background:rgba(0,0,0,.7);
    text-align: center;
    padding-top: 72px;
    color: white;
    display: none;
}
.case-box li:hover .span{
    display: block;
}
.case-box li img{
    width: 100%;
}