<html>
<head>
<style>
#main {
width: 70px;
height: 300px;
border: 1px solid #c3c3c3;
display: flex;
flex-flow: row wrap;
align-content: space-around;
}
#main div {
width: 70px;
height: 70px;
}
</style>
</head>
<body>
<div id="main">
<div style="background-color:coral;"></div>
<div style="background-color:lightblue;"></div>
<div style="background-color:pink;"></div>
</div>
<p><b>注意：</b>Internet Explorer、Firefox 和 Safari 不支持 align-content 属性。</p>
</body>
</html>