代码问题-求帮助
谁能告诉我，我这个问题出在哪里为什么没有反应呢？
<!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>无标题文档</title>
</head>
<body>
<script>
var btn2=document.getElementById('btn2');
btn2.addEventListener('click',showmesa,false);
function showmesa(){
alert('souw me');
}
</script>
<div id="box">
<input type="button" value="submit2" id="btn2">
</div>
</body>
</html>
