how to make a division center css

1position:absolute;
2top:50%;
3left:50%;
4transform:translate(-50%,-50%);
5

1<div id="outer">
2  <div id="inner">Foo foo</div>
3</div>
4//css:, demo with border
5<style>
6#inner {
7  display: table;
8  margin: 0 auto;
9  border: 1px solid black;
10}
11
12#outer {
13  border: 1px solid red;
14  width:100%
15}
16</style>

1margin:auto