Chromium 10.0.648.133 (77742) Ubuntu 10.10 にて動作確認した。
game.html
<html>
<head>
<script type="text/javascript" src="game.js"></script>
<title>game</title>
</head>
<body onload="draw();">
<canvas id="c1" width="640" height="480">
canvas is not available
</canvas>
</body>
</html>
game.js
function draw() {
var canvas = document.getElementById('c1');
if(canvas == null){
console.log("canvas is null");
return false;
}
var context = canvas.getContext('2d');
context.fillRect(0,0,20,20);
}