<style>
    canvas { border: solid green; }
</style>
<p>
    These should be two identical green hollow squares:
</p>
<canvas width="50" height="50"></canvas>
<canvas id="canvas"></canvas>
<script>
    document.body.offsetTop;
    var canvas = document.getElementById("canvas");
    canvas.setAttribute("width", 50);
    canvas.setAttribute("height", 50);
</script>