为什么这里CSS失效了？？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>字符串</title>
<style type="text/css">
p{
color:red;
background:#ccc;
}
</style>
</head>
<body>
<p>
段落<?php echo "444"."555"; ?>
</p>
</body>
</html>
