现场演示：我的 HTML 文档

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Example of Flex Items Alignment along Main Axis</title>
<style> 
.flex-container {
    width: 500px;
    min-height: 300px;
    margin: 0 auto;
	font-size: 32px;
    border: 1px solid #666;
    /* Safari */
    display: -webkit-flex;
    -webkit-justify-content: space-around;
    /* Standard syntax */
    display: flex;
    justify-content: space-around;
}
.flex-container div{
    padding: 10px;
}
.item1 {
    width: 75px;
    background: #e84d51;
}
.item2 {
    width: 125px;
    background: #7ed636;
}
.item3 {
    width: 175px;
    background: #2f97ff;
}
</style>
</head>
<body>
    <div class="flex-container">
        <div class="item1">1</div>
        <div class="item2">2</div>
        <div class="item3">3</div>
    </div>
    <p><strong>Note:</strong> Try the other values for the justify-content property like, "flex-start", "flex-end", "center" and "space-between" to understand how it aligns the items inside flex container.</p>
</body>
</html>