请问为何没有弹窗，也打不开网页
<!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 open(){
alert("欢迎来到慕课网");
window.open('http://www.imooc.com/','_blank','width=600, ,height=800');
}
</script>
</head>
<body>
<form>
<input type="button" value="点击我，打开新窗口" onclick="open()"/>
</form>
</body>
</html>
