W3Schools: "CSS Box Model, Border, Outline, Margin, and Padding"

Read these articles, which discuss the fundamentals of laying-out, organizing, and graphically formatting an HTML document using CSS depend on a thorough understanding of the element-box model.

After experimenting with the interactive elements on each of these pages, try to use the element-box model to modify the paragraphs, headings, tables, lists, and images you have included in your example webpage.