1. 我写了一段html5的代码，可是在浏览器中始终不能正常显示，是我js位置放的不对吗应该如何放
<!DOCTYPEhtml>
<html>
<head>
<metacharset="utf-8"/>
<title>书上例子的实践</title>
<scriptlanguage="javaScript"type="text/javascript">
functionAdd3()
{
varcanvas=document.getElementById("add3");
if(canvas)
{
varcontext=canvas.getContext("2d");
context.beginPath();
context.lineWidth=3;
context.moveTo(160,50);
context.lineTo(50,100);
context.lineTo(160,185);
context.fill();
}
}
window.onload=function(){
Add3();
}
</script>
</head>
<body>
<canvasheight="200"width="170"id="add3"></canvas>
</body>
</html>