Definition
Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in HTML or XML (including XML dialects such as SVG or XHTML). CSS describes how elements should be rendered on screen, on paper, in speech, or on other media.
Purpose and Use
CSS is primarily used to enhance the appearance of web pages by allowing designers and developers to apply visual styling and layout to HTML elements. It separates the content of a website (written in HTML or a similar markup language) from its visual design, making it easier to maintain and update the look of a website without altering the underlying content.
Key Features
- Selectors: CSS uses selectors to target HTML elements and apply styles to them.
- Properties: Each selector can contain one or more properties that define how the selected elements should be styled.
- Values: Properties are assigned values that dictate the specific styling, such as colors, fonts, sizes, margins, and more.
- Cascading: CSS rules cascade, which means that the priority of rules is determined by specificity, importance, and source order.
- Inheritance: Some CSS property values set on parent elements are inherited by their child elements, while others are not.
Syntax
A CSS rule consists of a selector and a declaration block:
selector {
property: value;
property2: value2;
}
For example, to set the text color of all <p> (paragraph) elements to blue, the CSS would look like this:
p {
color: blue;
}
Integration with HTML
CSS can be included in HTML documents in three ways:
- Inline Styles: Directly within an HTML element's
styleattribute. - Internal Stylesheet: Within a
<style>element in the<head>section of the HTML document. - External Stylesheet: In a separate
.cssfile linked from the HTML document using a<link>element.
Conclusion
Cascading Style Sheets (CSS) is a fundamental technology in web development, responsible for the visual style and layout of web pages. It provides a powerful and flexible means of creating attractive and consistent designs, while also allowing content to be accessible and legible on a wide range of devices. As web standards evolve, CSS continues to introduce new features and capabilities that enable more sophisticated and responsive designs.
