.evento1 {
    width: 100%;
    background: url('/it/slide/slide015.jpg') no-repeat center center;
    background-size: cover;
    float: left;
    z-index: 1;
}
.evento2 {
    width: 90%;
    margin-left: 5%;
    background: url('/it/slide/slide012.jpg') no-repeat center center;
    background-size: cover;
    float: left;
    z-index: 1;
}
.evento3 {
    width: 90%;
    margin-left: 5%;
    background: url('/it/slide/slide013.jpg') no-repeat center center;
    background-size: cover;
    float: left;
    z-index: 1;
}