alert写在哪里呢？这样子写显示不出对话框来
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>window对象</title>
<script type="text/javascript">
function openwin()
{
window.open("http://www.imooc.com","_blank","width=600px,height=400px");
alert("欢迎来到慕课学习JS")；
}
</script>
</head>
<body>
<form>
<input type="button" value="点击我，打开新窗口" onclick="openwin()"/>
</form>
</body>
</html>
