Edit in JSFiddle

<div class="demo-block">Demo Text</div>

/* Basic styles */
.demo-block {
    background-color: #ccc;
    color: #fff;
    padding: 25px;
}

/* Screen > 768px */
@media (min-width: 768px) {
    .demo-block {
        text-align: center;
    }
}

/* Screen > 992px */
@media (min-width: 992px) {
    .demo-block {
        text-align: right;
    }
}

/* Screen > 1200px */
@media (min-width: 1200px) {
    .demo-block {
        background-color: #fff;
        color: #000;
        text-align: left;
    }
}