em,vm,vh,and vw Units in CSS.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Some Units</title>
    <style>

        html{
            font-size: 36px;
        }
        h1{
            text-align: center;
        }
        

        .container{
            width:100vh;
            height:100vw;
            font-size: 10px;
            border:2px solid red;
        }
        #firstid{
            font-size: 3em;
            padding:3em
        }
        #secondid{
            font-size: 3rem;
            padding:3rem;
        }
        </style>
    </head>
<body>
    <div class="container">
       <h1 id="firstid"> This is First Heading</h1>
       <h1 id="secondid"> This is Second Heading</h1>
       <h1 id="thirdid"> This is Third Heading</h1>
       
    </div>
    
</body>
</html>