repeating-radial-1e.html
<div style="background: -moz-repeating-radial-gradient(closest-side, black 100px, black 150px, white 150px, white 200px); width: 400px; height: 400px;"></div>
<div style="background: -moz-repeating-radial-gradient(closest-side, black 100px, black 150px, white 150px, white 200px); width: 400px; height: 400px;"></div>