<!DOCTYPE html>
<html>
<head>
<style type="text/css" media="screen">
.box {
display: inline-block;
height: 200px;
width: 250px;
margin: 10px;
border: 1px solid black;
background-repeat: no-repeat;
}
.gradient1 {
background-image: radial-gradient(50% 50%, black, white);
}
.gradient2 {
background-image: repeating-radial-gradient(20% 20%, black, white, black);
}
</style>
</head>
<body>
<div class="gradient1 box"></div>
<div class="gradient2 box"></div>
</body>
</html>