Check out example codes for "centering css elements". It will help you in understanding the concepts better.

Code Example 1

.center {
  display: flex;
  justify-content: center;
  
  align-items: center;
  height: 200px;
  border: 3px solid 
  green; 
}

Code Example 2

<style>
.container {
  height: 200px;
  position: relative;
  border: 3px solid green;
}

.center {
  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  -ms-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}
</style>

<div class="container">
  <div class="center">
    <p>I am vertically and horizontally centered.</p>
  </div>
</div>

Code Example 3

.container{	
	margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  	width: /* Define the width here; */
    height: /* Define the height here; */
}

/*You have to define the width and height! */

Code Example 4

margin: auto;

Code Example 5

#inner {
  width: 50%;
  margin: 0 auto;
}

Code Example 6

// add to the parent element
.parent {
	display: grid;
    place-items: center;
}

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