<html>
<head>
<style>
#main {
width: 200px;
height: 200px;
border: 1px solid #c3c3c3;
display:flex;
flex-wrap: wrap;
}
#main div {
width: 50px;
height: 50px;
}
</style>
</head>
<body>
<div id="main">
<div style="background-color:coral;">A</div>
<div style="background-color:lightblue;">B</div>
<div style="background-color:khaki;">C</div>
<div style="background-color:pink;">D</div>
<div style="background-color:lightgrey;">E</div>
<div style="background-color:lightgreen;">F</div>
</div>
<p><b>注意：</b>Internet Explorer 和 Safari 不支持 flex-wrap 属性。</p>
</body>
</html>