<!DOCTYPE html>
<html>
    <body>
        <p>You should see two identical gray squares below</p>
        <svg width="600px" height="500px" xmlns="http://www.w3.org/2000/svg">
            <rect x="0" y="0" width="200" height="200" fill="rgba(0, 0, 0, 0.4)"/>
            <rect x="0" y="250" width="200" height="200" fill="rgba(0, 0, 0, 0.4)"/>
        </svg>
    </body>
</html>