                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript入门篇

求解哪里有错误，已经卡了好久。

<!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 open=confirm("新窗口打开网站");
      if(open==true)
      {
       var url=prompt("请输入网址","http://www.imooc.com");
       if(url!=null)
       {
           window.open(url,'_blank','witdh=400 height=500');
       }
       else
       {
           alert("null");
       }
       else
       {
           alert("null2")
       }
      }
}
</script>
</head>
<body>
   <input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>