Answers for "how to center content css"

center div horizontally and vertically

.parent {
  position: relative;
}
.child {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}

css align items vertical center

.parent {
  display: flex;
  justify-content: center;
  align-items: center;
}

align div content center

.child {
  ...
  margin: 0 auto;
}