<!DOCTYPE html>
<html>
    <head>
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <style>
            body, html {
                width: 100%;
                height: 100%;
                font-family: system-ui;
            }

            h2 {
                background: black;
                color: white;
                padding: 1em;
                display: inline-block;
            }

            div.red-box {
                width: 100px;
                height: 100px;
                background: red;
            }
        </style>
    </head>
    <body>
        <h2>This is some text</h2>
        <br>
        <img src="icon.png" />
        <div class="red-box"></div>
    </body>
</html>