JS部分onmousedown不起作用，大家帮忙看看
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
#box{
width: 400px;
height: 250px;
background-color: #F0FFFF;
border: solid cornflowerblue;
top: 200px;
left: 300px;
position: absolute;
}
#login{
width: 400px;
height: 30px;
border-bottom: solid cornflowerblue;
background-color: cornflowerblue;
margin-top:-18px;
}
#login p{
text-align: center;
color:#F0FFFF;
font-weight:900;
font-size: large;
}
</style>
<script type="text/javascript">
window.onload=drag;
function drag(){
var login=document.getElementById("login").childNodes[0];
login.onmousedown=fndown();
}
function fndown(){
document.onmousemove=function(event){
var box=document.getElementById("box");
box.style.left=event.clientX+'px';
box.style.top=event.clientY+'px';
}
}
</script>
</head>
<body>
<div id="box">
<div id="login"><p>登录</p></div>
</div>
</body>
</html>就是鼠标不用按下去，窗口都会跟着鼠标走
