.grid:after {
    content: '';
    display: block;
    clear: both;
}

.grid-sizer,
.grid-item {
    width: 33.333%;
}

@media (max-width: 575px) {

    .grid-sizer,
    .grid-item {
        width: 100%;
    }
}

@media (min-width: 576px) and (max-width: 767px) {

    .grid-sizer,
    .grid-item {
        width: 50%;
    }
}

.grid-item {
    float: left;
}

.grid-item img {
    display: block;
    max-width: 100%;
    margin: 8px;
}