div.adw300h250 {
    width: 300px;
    height: 250px;
    border: 1px solid gray;
    margin-left: auto;
    margin-right: auto;
    margin-block-end: 1em;
    max-width: 100%;
    height: auto;
}

div.adw600h100 {
    width: 600px;
    height: 100px;
    border: 0px;
    margin-left: auto;
    margin-right: auto;
    margin-block-start: 1em;
    margin-block-end: 1em;
    background-color: aquamarine;
    max-width: 100%;
    height: auto;
}