.scrollBox{
    box-sizing:border-box;

    overflow:auto;
}

.scrollBox:nth-of-type(3),
.scrollBox:nth-of-type(4){
    margin-top:0;
}
.contentBox1{
    width:100%;
    /*height:900px;*/
    /*background-image:url("../images/1.png");*/
    /*background-size:cover;*/
    /*background-repeat:no-repeat;*/
}
.contentBox2{
    width:1200px;
    height:100%;
    background-image:url("../images/2.png");
    background-size:cover;
    background-repeat:no-repeat;
}
.contentBox3{
    width:1200px;
    height:900px;
    background-image:url("../images/2.png");
    background-size:cover;
    background-repeat:no-repeat;
}