<html>
<head>
    <style type="text/css">
        html {
            border: 100px solid black;
        }
        #test {
            position: absolute;
            bottom: 0;
            right: 0;
            height: 200px;
            width: 200px;
            background: green;
        }
    </style>
</head>
<body>
  <div id="test">This should be in the bottom right-hand corner of the viewport even when resizing.</div>
</body>
</html>