Introduction to CSS

What is CSS? Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in HTML or XML. CSS controls the layout, colors, fonts, and overall appearance of web pages, enhancing user experience and accessibility. Why is CSS Important? History of CSS CSS was first proposed by Håkon Wium […]

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  • Post category: CSS
  • Reading time: 22 mins read
  • Post last modified: April 3, 2025

What is CSS?

Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in HTML or XML. CSS controls the layout, colors, fonts, and overall appearance of web pages, enhancing user experience and accessibility.

Why is CSS Important?

  • Separation of Concerns: CSS separates content (HTML) from design, making code more maintainable.
  • Consistency: Ensures a uniform look across multiple pages.
  • Efficiency: Reduces code duplication and improves page loading speed.
  • Responsive Design: Enables web pages to adapt to different screen sizes.
  • Accessibility: Enhances user experience for people with disabilities.

History of CSS

CSS was first proposed by Håkon Wium Lie in 1994 and officially released as CSS1 in 1996. Since then, it has evolved through multiple versions:

  • CSS1 (1996): Basic styling options (colors, fonts, margins).
  • CSS2 (1998): Added positioning, media types, and more.
  • CSS3 (2011+): Introduced modular features like animations, transitions, and flexbox.

Basic Structure of CSS

A CSS rule consists of a selector and a declaration block:

Copy
selector {
  property: value;
}
CSS

Example:

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p {
  color: blue;
  font-size: 16px;
}
CSS

This rule applies blue color and 16px font size to all <p> elements.

How Browsers Interpret CSS

Web browsers parse CSS to apply styles to elements in the Document Object Model (DOM). The rendering process involves:

  1. Parsing: The browser reads CSS and converts it into a structure.
  2. Styling: Styles are assigned to elements.
  3. Layout Calculation: The browser determines where elements are placed.
  4. Painting & Compositing: The final visual representation is displayed.

CSS and HTML Together

CSS is used alongside HTML to enhance web pages. Without CSS, websites would appear as plain text and unstructured content.

Example:

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Example</title>
    <style>
        body {
            background-color: lightgray;
            text-align: center;
        }
    </style>
</head>
<body>
    <h1>Welcome to CSS</h1>
    <p>This is a styled paragraph.</p>
</body>
</html>
HTML

Conclusion

CSS is an essential technology for modern web development. It enhances the design, usability, and responsiveness of websites. In the upcoming sections, we will explore CSS syntax, selectors, the box model, and advanced styling techniques.

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