为什么我按老师的代码写没有效果
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
.container{background:#ddd;width:500px;height:250px;}
</style>
</head>
<body>
<div class="container"></div>
<script src="http://d3js.org/d3.v3.js"></script>
<script>
d3.select("container").append("svg:svg");
</script>
</body>
</html>
