CSS, or Cascading Style Sheets, is a stylesheet language used to describe the look and formatting of a document written in a markup language. It is most commonly used to style web pages written in HTML and XHTML, but can also be used to format documents written in XML-based languages.
CSS allows web developers to create visually appealing and consistent websites quickly and easily. It is a powerful tool for controlling the presentation of content on the web, and is essential for building modern and responsive websites.
CSS is a declarative language, which means that it uses a series of statements or declarations to define how elements on a web page should be styled. These declarations are made up of two parts: the selector, which identifies the element or elements to be styled, and the declaration block, which specifies the styles to be applied to the selected elements.
For example, the following CSS declaration would change the font color of all of the h1 elements on a web page to red:
h1 {
color: red;
}
CSS has a wide range of features and capabilities, including the ability to control text and font properties, colors and backgrounds, margins and padding, positioning and layout, and many other visual aspects of a web page. It also supports media queries, which allow developers to create styles that are tailored to different devices and screen sizes.
In addition to its core features, CSS also has a number of advanced features and capabilities, including the ability to create complex layouts using Flexbox and Grid, to animate elements using transitions and keyframes, and to create custom interactive user interfaces using the CSS pseudo-classes and pseudo-elements.
CSS has become an essential part of modern web development, and is widely used by web designers and developers around the world. It provides a simple and flexible way to create visually appealing and consistent websites, and is an essential tool for building modern and responsive web applications.