请大神帮我看看，不知道哪里错了，符号也是英文状态下输入的，不弹出对话框
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>我们互动下</title>
<script type="txt/javascript">
function dhk(){
var mymessage=confirm("关注JS高级篇！");
if(mymessage==true){
document.write("加油！");
}
else{
document.write("期待您的关注！");
}}
</script>
</head>
<body>
<form>
<input type="button" value="JS进阶篇" onclick="dhk()">
</form>
</body>
</html>
