                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript入门篇

这个怎么回事？死活不行呢？

<!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 openwin = confirm("是否打开新窗口？");
    if(openwin)
    {
        var myweb = prompt("请输入你要打开的网址："," http：//www.imooc.com/");
       if(myweb!=null)
       {
           window.open('http：//www.imooc.com/',width=400,height=500);
       }

   }
    }

</script>
</head>
<body>
      <input type="button" value="新窗口打开网站" onclick="openwindow()" />
</body>
</html>