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Lesson 81: Introduction to Responsive Web Design (RWD)

CSS Mastery: From Zero to Hero in 100 Lessons

81. Introduction to Responsive Web Design (RWD)

Responsive Web Design is the practice of building a website that adapts its layout, appearance, and functionality to various screen sizes, orientations, and resolutions (from phones to large desktops).

Core Principles of RWD

  1. Fluid Grids: Using relative units (%, fr, vw) rather than fixed pixels for primary layout dimensions.
  2. Flexible Images: Ensuring media scales within containers.
  3. Media Queries: The primary tool used to apply specific CSS rules only when certain conditions (like screen width) are met.

The Viewport Meta Tag (Crucial Setup)

For a responsive site to work correctly on mobile devices, you must include the viewport meta tag in the HTML <head>.

Without this tag, mobile browsers assume a large desktop width (e.g., 980px) and scale the whole page down, which is the opposite of responsive design.

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Rule: Always start a new responsive project by adding this meta tag.