<script type="text/javascript">
function openwindow()
{
 var m1=confirm("是否打开窗口");
 if(m1=="true")
 {
  var n2=prompt("请输入网址","http://www.imooc.com/");
  if(n2!='null')
  {
   window.open(n2,"_blank","width=400,height=500,menubar=no,toolbar=no");
  
  } 
  else
   {
   alert("再见");
   }

 }
                      else
                {
        alert("下次再见");
       }
}
</script>