.red-blinking {
    -webkit-animation: 1s blink ease infinite;
    -moz-animation: 1s blink ease infinite;
    -ms-animation: 1s blink ease infinite;
    -o-animation: 1s blink ease infinite;
    animation: 1s blink ease infinite;
    border-radius: 50%;
    width: 16px;
    height: 16px;
    background: red;
    display: inline-block;
    vertical-align: sub;
    border: 3px solid darkred;
    box-sizing: content-box;
}

@keyframes blink {
    from, to {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
}

@-moz-keyframes blink {
    from, to {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
}

@-webkit-keyframes blink {
    from, to {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
}

@-ms-keyframes blink {
    from, to {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
}

@-o-keyframes blink {
    from, to {
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
}