<!DOCTYPE html> <html> <style> html, body { margin: 0; padding: 0; } </style> <body> <canvas id ="canvas" width="50" height="20" style="position:relative; top:40px; left:50px"></canvas> <script> var canvas = document.getElementById('canvas'); var context = canvas.getContext("2d"); context.fillStyle = 'green'; context.fillRect(0, 0, 50, 20); </script> </body> </html>