CSS3 Pulsating Ring

content.css

.ring {
    border: 3px solid #999;
    -webkit-border-radius: 30px;

    height: 40px;
    width: 40px;

    position: fixed;
    top: 45%;
    left: 45%;

    animation: pulse 1s ease-out infinite;
    -webkit-animation: pulse 1s ease-out infinite;
    -moz-animation: pulse 1s ease-out infinite;

    opacity: 0.0
}

@keyframes pulse {
    0% { transform: scale(0); opacity: 0.0; }
    50% { opacity: 1.0; }
    100% { transform: scale(1.2); opacity: 0.0; }
}
@-webkit-keyframes pulse {
    0% { -webkit-transform: scale(0); opacity: 0.0; }
    50% { opacity: 1.0; }
    100% { -webkit-transform: scale(1.2); opacity: 0.0; }
}
@-moz-keyframes pulse  {
    0% { -moz-transform: scale(0); opacity: 0.0; }
    50% { opacity: 1.0; }
    100% { -moz-transform: scale(1.2); opacity: 0.0; }
}