how to align in the middle of a div css code example

Example 1: center a div in css

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

Example 2: css center

// example 1 
div { display: grid; place-items: center; }

// example 3
div{ display:flex; align-items:center; }

// example 3
div { width: 100%; margin: 0 auto; }