CSS Introduction

Last reviewed May 28, 2026 Content v20260528

This lesson

An orientation to this CSS lesson—scope, vocabulary, and what you will practice next.

You need a clear map of the CSS track so later lessons do not feel like isolated tricks.

You will apply CSS Introduction in contexts like: All browser UIs, component libraries, marketing sites, and many native apps that reuse web views.

Read the lesson, edit HTML/CSS in the playground, press Run to preview, then answer the lesson MCQs. Also open the interview prep blocks.

Start here at the beginning of the css track before skipping ahead.

CSS (Cascading Style Sheets) applies style rules to HTML elements selected from the DOM tree.

A paragraph can inherit font styles from body while receiving color from a class rule.

Q: What does “cascading” mean?
A: Multiple matching rules are merged using precedence rules.
Q: What is inheritance in CSS?
A: Some properties naturally flow from parent to child (for example text-related properties).
Q: Why is CSS debugging hard for beginners?
A: Because many rules can apply simultaneously and hide each other.

Pitfall: Check cascade order—author stylesheet loses to inline styles and !important surprises.

Can you explain this lesson in 30 seconds without reading notes?

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