Check out this HTML5 SVG code for creating concentric circles:
<!DOCTYPE html>
<html>
<body>
<div style="margin-left:100px;">
<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
<circle cx="400" cy="400" r="200" stroke="black" class='yellow_cir' stroke-width="2" fill="red" />
<circle cx="400" cy="400" r="150" stroke="black" class='yellow_cir' stroke-width="2" fill="yellow" />
<circle cx="400" cy="400" r="100" stroke="black" class='yellow_cir' stroke-width="2" fill="cyan" />
<circle cx="400" cy="400" r="50" stroke="black" class='yellow_cir' stroke-width="2" fill="cyan" />
<defs>
<radialGradient id="grad1" cx="50%" cy="50%" r="50%" fx="50%" fy="50%">
<stop offset="0%" style="stop-color:rgb(255,255,255);
stop-opacity:1" />
<stop offset="100%" style="stop-color:rgb(100,100,105);stop-opacity:1" />
</radialGradient>
<radialGradient id="grad2" cx="50%" cy="50%" r="50%" fx="50%" fy="50%">
<stop offset="0%" style="stop-color:rgb(255,255,255);
stop-opacity:1" />
<stop offset="100%" style="stop-color:rgb(10,10,105);stop-opacity:1" />
</radialGradient>
</defs>
</svg>
</div>
</body>
</html>
<style type="text/css">
.yellow_cir:hover{ fill:url("#grad2");cursor:pointer;
}
.yellow_cir
{
fill:url("#grad1");
}
</style>