<script>
window.onload = function() {
var canvas = document.getElementById('quadro');
var ctx = canvas.getContext('2d');
ctx.strokeStyle = '#f00';
ctx.lineWidth = 2;
ctx.strokeRect(30,30, 80,40);
ctx.strokeStyle = '#00f';
ctx.lineWidth = 4;
ctx.strokeRect(130,100, 140,90);
ctx.strokeStyle = '#000';
ctx.lineWidth = 2;
ctx.fillStyle = 'rgba(0,255,0,0.4)';
ctx.fillRect(150,60, 200,70);
ctx.strokeRect(148,58, 204,74);
}
</script>
canvas {border:1px solid #ccc;}
<canvas id="quadro" width="400" height="200"> <p>Conteúdo alternativo para navegadores que não suportam canvas.</p> </canvas>