CSS Introduction

CSS (Cascading Style Sheets) is a style sheet language used to describe the presentation style of web documents. Together with HTML and JavaScript, it constitutes the three core technologies of modern web development. The main function of CSS is to control the appearance and format of web pages by defining styles and layouts, thereby enhancing the user experience.

The basic goal of CSS is to separate content from presentation, making web development more efficient and flexible. By using CSS, developers can apply styles uniformly on multiple web pages without repeating style definitions in each HTML file. This separation not only simplifies code management, but also makes it easier to maintain and update web pages.

CSS uses the syntax of selectors and declaration blocks to define styles. Selectors are used to select HTML elements to apply styles, while declaration blocks contain a series of attributes and their corresponding values, such as fonts, colors, margins, and layouts. CSS allows developers to define styles in a cascading manner, that is, multiple styles can be applied to the same element, and the priority and characteristics of these styles are determined by their source and definition order.

CSS provides a rich range of style properties, covering text styles, box models, backgrounds, borders, layouts, animations, and transitions. Developers can precisely control the visual effects of web pages by setting these properties. For example, using CSS's Flexbox and Grid layout models, developers can easily create responsive and dynamic web page layouts to adapt to different screen sizes and devices.

As CSS develops, new standards and features are constantly introduced. For example, CSS3 enhances support for animations, transformations, and media queries, allowing developers to create richer and more interactive user interfaces. In addition, CSS preprocessors such as SASS and LESS also make stylesheet writing more flexible, supporting features such as variables, nesting, and functions.

In short, CSS is a powerful style sheet language that greatly enhances the power and flexibility of web design. By controlling the visual presentation of web pages, CSS enables developers to create beautiful, easy-to-use user interfaces and provide users with a better browsing experience. With the continuous advancement of web technology, mastering CSS has become a basic skill in web development.