body {
    margin:0px;
}

.content{
    width:100%;
    height:100vh;
    background-image:url(../img/building_mobile.jpg);
    background-position:center;
    background-size:cover;
}

/* Small devices (tablets, 768px and up) */
@media (min-width: 768px) {
    .content {
        width: 100%;
        height: 100vh;
        background-image: url(../img/building_web.jpg);
        background-position: center;
        background-size: cover;
    }
}

/* Medium devices (desktops, 992px and up) */
@media (min-width:992px) {
    .content {
        width: 100%;
        height: 100vh;
        background-image: url(../img/building_web.jpg);
        background-position: center;
        background-size: cover;
    }
}

/* Large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
    .content {
        width: 100%;
        height: 100vh;
        background-image: url(../img/building_web.jpg);
        background-position: center;
        background-size: cover;
    }
}