.status-led {
    display: inline-block;
    width: 20px;
    height: 20px;
    background-size: 100%;
    background-position: center center;
    background-repeat: no-repeat;
    vertical-align: middle;
}

.status-led.on {
    background-image: url("../img/status-on.png");
}

.status-led.off {
    background-image: url("../img/status-off.png");
}

.status-led.error {
    background-image: url("../img/status-error.png");
}