div{
    height: 700px;
    width: 100px;
    margin: 1px;
    position: absolute;
    background-color: antiquewhite;
    opacity: 0.8;
}

.bloc1{
    margin-left: 100px;
    opacity: 0.7;
}

.bloc2{
    margin-left: 200px;
    opacity: 0.5;
}

.bloc3{
    margin-left: 300px;
    opacity: 0.3;
}

.bloc4{
    margin-left: 400px;
    opacity: 0.2;
}