为什么我这个点取消还会出现网页？
<!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 mymessage=confirm("确认打开网址？");
if(mymessage=true){
window.open('http://www.imooc.com','_blank','width=400,height=500,menubar=no,toolbar=no');
}
else
{
alert("打开失败！");
}
}
</script>
</head>
<body>
<input type="button" value="新窗口打开网站" onclick="openWindow()" />
</body>
</html>
