VERTICALLY CENTER ALIGN TEXT USING TRANSFORM PROPERTY
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>HTML</title>
<style>
    .container {
	  height: 200px;
	  width: 500px;
	  position: relative;
	  border: 3px solid green;
      }
	.center {
	  margin: 0;
	  position: absolute;
	  top: 50%;
	  -ms-transform: translateY(-50%);
	  transform: translateY(-50%);
	  }
</style>
</head>
<body>
    <div class="container">
      <div class="center">Vertically center align text within div element using Flexbox</div>
	</div>
</body>
</html>