senter element css

1div.container4 {
2    height: 10em;
3    position: relative }
4div.container4 p {
5    margin: 0;
6    background: yellow;
7    position: absolute;
8    top: 50%;
9    left: 50%;
10    margin-right: -50%;
11    transform: translate(-50%, -50%) }
12
13IMG.displayed {
14    display: block;
15    margin-left: auto;
16    margin-right: auto }
17...
18<IMG class="displayed" src="..." alt="...">
19