ลองตัวเอง - CSS Reference js

<!DOCTYPE html>
<html>
<head>
<style> 
#main {
    width: 140px;
    height: 300px;
    border: 1px solid #000000;
    display: -webkit-flex; /* Safari */
    -webkit-flex-wrap: wrap; /* Safari 6.1+ */
    -webkit-align-content: space-around; /* Safari 7.0 */
    display: flex;
    flex-wrap: wrap;
    align-content: space-around; 
}

#main div {
    width: 70px;
    height: 70px;
}
</style>
</head>
<body>

<p>Click the "Try it" button to set the value of the alignContent property to "space-between"</p>
<button onclick="myFunction()">Try it</button>

<p><b>Note:</b> Internet Explorer 10 and earlier versions do not support the alignContent property.</p>

<p><b>Note:</b> Safari 7.0 (and newer) supports an alternative, the WebkitAlignContent property.</p>

</body>
</html>