html运行实例（css3_flexbox_margin

代码示例：（标识：css3_flexbox_margin_2）

<!DOCTYPE html>
<html>
<head>
<style> 
.flex-container {
  display: -webkit-flex;
  display: flex;
  width: 400px;
  height: 250px;
  background-color: lightgrey;
}

.flex-item {
  background-color: cornflowerblue;
  width: 75px;
  height: 75px;
  margin: auto;
}
</style>
</head>
<body>

<div class="flex-container">
  <div class="flex-item">完美的居中！</div>
</div>

</body>
</html>