This example displays the text "Hello HTML!" centered on the page, styled with a large 13-em font size via the `.message` CSS class. It demonstrates a minimal static web page using pure HTML and CSS, with no JavaScript functionality. The rendering relies on the browser’s default layout engine to position and display the text block. The styling is defined inline within the `<style>` tag, while the content resides in the `<body>` element, showcasing the basic separation of structure and presentation.