What is CSS?

CSS (.css) files contain Cascading Style Sheets code that controls the visual presentation of HTML documents. CSS defines colors, layouts, fonts, animations, and responsive behaviors. Modern CSS3 includes flexbox, grid, custom properties (variables), and powerful animations.

CSS enables separation of content and presentation, allowing designers to change the look of entire websites by editing a single stylesheet. It's essential for creating responsive, accessible, and beautiful web experiences.

Did you know? CSS Grid and Flexbox revolutionized web layouts, eliminating the need for complex float-based hacks!

History

CSS was proposed by Håkon Wium Lie in 1994 to solve the problem of styling web documents. It has evolved from basic text styling to a powerful layout and animation system.

Key Milestones

  • 1996: CSS1 released
  • 1998: CSS2 with positioning and media types
  • 2011: CSS3 modular specifications
  • 2017: CSS Grid Layout support
  • 2020s: Container queries and advanced features

Key Features

Core Capabilities

  • Selectors: Target elements by class, ID, attribute
  • Flexbox: One-dimensional layouts
  • Grid: Two-dimensional layouts
  • Animations: Transitions and keyframe animations
  • Custom Properties: CSS variables
  • Media Queries: Responsive breakpoints

Common Use Cases

Responsive Design

Mobile-first layouts

Visual Styling

Colors, fonts, spacing

Animations

Transitions and effects

Print Styling

Optimized for printing

Advantages

  • Separation of content and presentation
  • Powerful layout systems (Grid, Flexbox)
  • Responsive design capabilities
  • No JavaScript needed for styling
  • Reusable stylesheets
  • Browser optimizations

Disadvantages

  • Browser compatibility issues
  • Cascade specificity conflicts
  • No scoping by default
  • Limited logic (needs preprocessors)
  • Naming conventions required

Technical Information

Format Specifications

Specification Details
File Extension .css
MIME Type text/css
Format Type Stylesheet Language
Encoding UTF-8
Current Version CSS3 (Modular)
Maintained by W3C

Common Tools

  • Preprocessors: Sass, Less, Stylus
  • Frameworks: Bootstrap, Tailwind
  • Linters: Stylelint, CSS Lint