CSS

CSS, or Cascading Style Sheets, is a style sheet language used for describing the presentation of a document written in HTML or XML. It allows for the separation of content from presentation, enabling web developers to control the layout, colors, fonts, and other visual aspects of web pages. CSS was first proposed by Håkon Wium Lie in 1994 and has since become an essential technology for web design.

CSS works by associating rules with HTML elements. A CSS rule consists of a selector and a declaration block. The selector targets the HTML elements to be styled, while the declaration block contains one or more declarations, each specifying a property and its value. For example, the rule "p { color: blue; }" targets all paragraph elements and sets their text color to blue.

CSS can be applied to HTML documents in three ways: inline, internal, and external. Inline styles are applied directly to HTML elements using the style attribute, while internal styles are defined within a style element in the HTML document's head section. External styles are stored in separate CSS files and linked to HTML documents using the link element.

CSS supports inheritance, where certain properties are inherited by child elements from their parent elements. It also supports cascading, where multiple CSS rules can apply to the same element, and the browser determines which rule takes precedence based on specificity, importance, and source order.

CSS has evolved over the years, with new features and improvements introduced in each version. The most recent version, CSS3, includes modules for advanced layout, typography, animations, and more. CSS is widely supported by web browsers and is an integral part of modern web development.