.banner_op {
    opacity: 0.15
}

    .banner_op:hover {
        opacity: 1
    }

img {
    opacity: 0.25;
}

    img:hover {
        opacity: 1
    }

.banner_op {
    position: absolute;
    right: 100px;
    width: 200px;
    height: 120px;
}

.mydiv {
    border: 5px solid gray;
    background-color: transparent;
    text-align: center;
    margin-top: 250px;
    margin-left: auto;
    margin-right: auto;
    height: 270px;
    width: 400px;
    position: absolute, center;
    block-size: auto;
}