CodeMirror: HTML5 preview

<!doctype html>
<!doctype html>
<html>
  <head>
    <meta charset=utf-8>
    <title>HTML5 canvas demo</title>
    <style>p {font-family: monospace;}</style>
  </head>
  <body>
    <p>Canvas pane goes here:</p>
    <canvas id=pane width=300 height=200></canvas>
    <script>
      var canvas = document.getElementById('pane');
      var context = canvas.getContext('2d');
 
      context.fillStyle = 'rgb(250,0,0)';
      context.fillRect(10, 10, 55, 50);
 
      context.fillStyle = 'rgba(0, 0, 250, 0.5)';
      context.fillRect(30, 30, 55, 50);
    </script>
  </body>
</html>