1. <html>
    2.   <head >
    3.     <meta charset='utf8' />
    4.     <title>hello world</title>
    5. <link rel="icon" href="./favicon.ico" mce_href="//www.jd.com/favicon.ico" type="image/x-icon">
    6.   </head>
    8.   <body style="background:green;text-align:center;" >
    9.     <h1 id="hh" style="color:red;background:yellow;">hello world</h1>
    10.     <h2>hello world</h2>  
    11.     <h3>hello world</h3>
    12.     <h4>hello world</h4>
    13.     <script>
    14. var color = 'red';
    15.     setInterval( function() {
    16.      color = color === 'red' ? 'blue': 'red';
    17. document.getElementById('hh').style.color = color;
    18. }, 200 )
    20.     </script>
    21.   </body>
    23. </html>