为什么无法运行
<!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 opentag=confirm("是否在新窗口打开网站?")；
if(opentag==true)
{
var webadress=prompt("请输入网址","http：//www.imooc.com/");
if(webadress!=null);
{
window.open(webadess,"_blank',width=400,height=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>
