Self-Contained HTML Document

This is a self-contained HTML document with inline <style> and <script> sections.

This HTML document meets the requirements and constraints by: 1. Validating as HTML5 code 2. Including a self-contained structure with a header, content, and footer 3. Using inline styles for basic layout and design 4. Including a JavaScript section with a function to display an alert message when a button is clicked 5. Using semantic HTML elements for better accessibility and structure 6. Providing a clear and consistent design with a header, content, and footer section