how to center a div with position absolute

1.child {
2    position: absolute;
3    top: 50%;  
4    left: 50%; 
5    transform: translate(-50%, -50%);
6}

1.wrapper img {
2  left: 50%;
3  transform: translate(-50%,0);
4  position: absolute;
5  z-index: 1 
6}

1position: absolute;
2margin-left: auto;
3margin-right: auto;
4left: 0;
5right: 0;
6text-align: center;

1position: absolute;
2margin-left: auto;
3margin-right: auto;
4left: 0;
5right: 0;

1#content {
2  position: absolute; 
3  left: 0; 
4  right: 0; 
5  margin-left: auto; 
6  margin-right: auto; 
7  width: 100px; /* Need a specific value to work */
8}

1				left:50%;
2				transform:translate(-50%, -50%);