My code is not working on cloud 9 but in other platforms it's working properly

html
css

#1
<style type ="text/css">

    body {background-color:#6495ed;}
    .odd {background-color:#000000;text-align: center;}
    .odd h1 {color:#ff0000;font-size: 20px;}
    
    .even {background-color: #ff0000;text-align:center;}
    .even h1{color:#ffffff;font-size: 20px;}
    h1{font-style: sans-serif;}
style
<body>
    <div class="odd">
        <h1>1</h1>
        <h1>3</h1>
        <h1>5</h1>
        <img src="http://media.philly.com/images/companions_adelie_penguins.jpg" width="150">
    </div>
    <div class="even">
        <h1>2</h1>
        <h1>4</h1>
        <h1>6</h1>
        
        <img src="http://media.philly.com/images/companions_adelie_penguins.jpg" width="150">
    </div>
    
</body>

</html>