CSS Documentation

This guide introduces CSS (Cascading Style Sheets) fundamentals, focusing on concepts and best practices for developers using the Codeunia Learn platform.

Overview

CSS is a style sheet language used to describe the presentation of HTML documents. It controls layout, colors, fonts, and responsiveness, enabling visually appealing and user-friendly web interfaces. CSS3 introduces advanced features like animations and flexbox.

CSS Fundamentals

Selectors

Selectors target HTML elements for styling. Types include element selectors (p), class selectors (.class), ID selectors (#id), and attribute selectors.

Properties and Values

CSS properties define styles (e.g., color, font-size). Values can be keywords, lengths, percentages, or colors.

Box Model

Every element has content, padding, border, and margin. Understanding the box model is crucial for layout.

Units

Units include pixels (px), ems (em), rems (rem), percentages (%), and viewport units (vw, vh).

Layout Techniques

Flexbox

Flexbox provides flexible layouts with properties like display: flex, justify-content, and align-items.

Grid

CSS Grid creates complex layouts with display: grid, grid lines, and areas.

Positioning

Positioning uses static, relative, absolute, fixed, and sticky values.

Typography

Font properties include font-family, font-size, font-weight, and line-height. Web fonts are loaded with @font-face.

Colors and Backgrounds

Colors use hex, RGB, HSL, or named values. Backgrounds support images, gradients, and multiple layers.

Responsive Design

Media queries adapt styles for different screen sizes. Mobile-first design is recommended.

Animations and Transitions

Transitions smoothly change properties. Keyframes define complex animations.

CSS Variables

Custom properties (variables) enable reusable values and dynamic theming.

Specificity and Cascade

CSS rules cascade; specificity determines which rules apply. Use !important sparingly.

Best Practices

Organize CSS with methodologies like BEM or SMACSS. Minimize specificity conflicts and optimize for performance.

Frameworks and Preprocessors

Frameworks like Bootstrap accelerate development. Preprocessors like Sass extend CSS with variables and functions.

Browser Compatibility

Use vendor prefixes and tools like Autoprefixer for cross-browser support.

Resources and References

• MDN CSS Documentation
• CSS Tricks
• Can I Use

Troubleshooting

Common issues include layout breaks, specificity wars, and cross-browser inconsistencies. Browser dev tools debug styles.

Development Setup

Use a code editor with CSS support, preview in browsers, and test responsiveness. Build tools like PostCSS enhance workflows.