div不显示

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
		<style>
			#box{
				width: 200px;
				height: 200px;
				background: red;
			}
		</style>
	</head>
	<body>
		<center>
			<label class="a1" title="测试">合同id</label>
			<label class="a1" title="测试1">合同id-1</label>
			<div id="box">哈哈哈哈</div>
		</center>
		
	</body>
	
	<script>
		document.getElementById("box").style.display="none"
	</script>
</html>