Untitled

<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
        <title>pulse</title>
        <style>
            @keyframes glow-pulse {
                0%  { opacity: 0.5; }
                60% { opacity: 1.0; }
                100% { opacity: 0.5; }
            }

            .pulse {
                width: 100px;
                height: 100px;
                border-radius: 100%;
                background-color: #609;
                animation: glow-pulse 1s infinite;
            }
        </style>
    </head>
    <body>
        <div class="pulse"></div>
    </body>
</html>