<!DOCTYPE html>
<html>
<body>
<p><strong>Note:</strong> This example does not work in Internet Explorer and Safari.</p>
<svg width="400" height="400">
<rect x="20" y="20" width="250" height="250" style="fill:blue">
<animate attributeType="CSS" attributeName="opacity" from="1" to="0" dur="5s" repeatCount="indefinite" />
</rect>
Sorry, your browser does not support inline SVG.
</svg>
</body>
</html>