how to position a element in center in css code example

Example 1: css align center

//HTML
<div class="parent">
	<span>Hello World</span>
</div>

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

Example 2: image center in div

img {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 40%;
}