HTML5 Canvas Transparency

<!DOCTYPE html>
<html>
<head>
<title>HTML5 Canvas Transparency</title>
</head>
<body>
<canvas id="MyCanvas" width="650" height="600"></canvas>
<script>
var canvas = document.getElementById("MyCanvas");
if (canvas.getContext) // Test for support.
  {
    var ctx = canvas.getContext("2d"); // Get the context to draw on.
      for (var g = 0,x=0, y=25; g <= 10; g+=1, x+=25, y+=25)
       {
         ctx.globalAlpha = g/10;
         ctx.fillStyle = "red";
         ctx.strokeStyle = "black";
         ctx.fillRect(x, y, 200, 200);  // Create a filled rectangle.
         ctx.strokeRect(x, y, 200, 200); // Put an outline around it
         ctx.globalAlpha = 1;
         ctx.fillStyle = 'blue';
         ctx.font = "14px Unknown Font, sans-serif";
         ctx.fillText(" Transparency Value "+g, 202+x, y+10);
         ctx.globalAlpha = g/10;
       }
  }
</script>
</body>
</html>