这样写对么？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<div id="con">
<p>javascript</p>
<div>jQuery</div>
<h5>PHP</h5>
</div>
<script type="text/javascript">
var x=document.getElementById("con");
document.write(x.firstChild+"<br>");
document.write(x.lastChild);
</script>
</body>
</html>
