<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>style样式</title>
</head>
<body>
<h2 id="con">I love JavaScript</H2>
<p> JavaScript使网页显示动态效果并实现与用户交互功能。</p>
<script type="text/javascript">
var mystr=document.getElementById("con");
mystr.style.color="red";
mystr.style.backgroundColor="#CCC";
mysty.style.display="none";
</script>
</body>
</html>
隐藏啊，你自己打错字才没效果
错 mysty.style.display="none";
对 mystr.style.display="none";