test2.html

 
<!DOCTYPE>
<html>
<head>
    <meta name="charset" content="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title></title>
    <link href="//cdnjs.cloudflare.com/ajax/libs/normalize/3.0.1/normalize.min.css" rel="stylesheet" type="text/css">
    <link href="//fonts.googleapis.com/css?family=Roboto:400,300,700" rel="stylesheet" type="text/css">
    <style>
        body {
            width: 960px;
            margin: 0 auto;
        transition: all 1s ease;
        }
    </style>
</head>
<body>
    <header><h1></h1></header>
​
    <main></main>
​
    <footer></footer>
​
    <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
    <script>
      //setTimeout(function() {}, 1000);
      $('body').css('background', 'black')
      setTimeout(function() {$('body').css('background', 'white')}, 2000);
    </script>
</body>
</html>