我这个哪里不对
<html>
<head>
<title> new document </title>
<meta http-equiv="Content-Type" content="text/html; charset=gbk"/>
<script type="text/javascript">
function openwindow(){
var open=confirm("确认打开新窗口吗");
if(open=true)
{var url=prompt("请输入一个网址","http://www.imooc.com/");
if(url!=null)
{window.open(url,'_blank','width=400,heigth=500,menubar=no,toolbar=no')}
else
{alert("结束");}
}
else
{alert("结束");}
}
</script>
</head>
<body>
<input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>