css display contents

1.a {
2  display: contents;
3  border: 2px solid red;
4  background-color: #ccc;
5  padding: 10px;
6  width: 200px;
7}
8
9.b {
10  border: 2px solid blue;
11  background-color: lightblue;
12  padding: 10px;
13}