How CSS Shapes Modern Web Pages

This lesson introduces CSS as the presentation layer of the web: the language that turns structured HTML into readable, usable, visually organized pages. Students learn how CSS rules target elements, how declarations change appearance, and why separating content from presentation is essential for maintainable websites.

The lesson focuses on the core mental model needed before responsive design: selectors, the cascade, inheritance, specificity, the box model, layout flow, and browser defaults. By the end, students should be able to look at a simple web page and explain how CSS is shaping its typography, spacing, color, and layout behavior.