为什么不能获取元素？
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www. >
<html xmlns="http://www. xml:lang="en" lang="en" >
<head>
<title>My Prototype test bench</title>
<script type="text/javascript">
var t=document.getElementById("temp");
alert(t);
</script>
</head>
<body>
<div id="temp">
Hellow world!
</div>
</body>
</html>
运行为null
