body
{
}
.banner {
    margin: 300px auto 0 auto;
    min-height: 420px;
    max-width: 420px;
    padding: 40px;
    background-color: #ffffff;
    margin-left: auto;
    margin-right: auto;
    border-radius: 4px;
    /* overflow-x: hidden; */
    box-sizing: border-box;
}
    .banner>img {
        width: 300px;
        height: 300px;
    }