js加在head里dom0级事件分明不起作用啊？（
<!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> <script type="text/javascript">
<!--
var button2=document.getElementById("botton2");
function min() {
alert("这是第二个按钮")
};
button2.addEventListener('click',min,false);
button2.addEventListener('click',function(){
alert(1)
},false);
botton2.removeEventListener('click',min,false);
/-->
</script>
</head>
<body>
<input name="" type="button" value="这是第一按钮" id="botton"/>
<input name="" type="button" value="这是第二按钮" id="botton2" />
</body>
</html>
js加在head里dom0级事件分明不起作用啊？（SCRIPT5007: 无法获取属性“addEventListener”的值: 对象为 null 或未定义
addEventcistener.html, 行11 字符2）
