为什么网页打不开？
<!DOCTYPE html>
<html>
<head>
<title> new document </title>
<meta http-equiv="Content-Type" content="text/html; charset=gbk"/>
<script type="text/javascript">
function openWindow(){
var window=confirm("新窗口打开网站");
if(window==true){
var http = prompt("请输入网站地址","http://www.imooc.com");
if(http!=null){
window.open(url,"_blank","width=400px,height=500px,menubar=no,tolbar=no");
}else{
alert("88");
}
}else{
alert("88");
}
}
</script>
</head>
<body>
<input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>
