what is css

CSS is the abbreviation of Cascading Style Sheet, which is a language used to describe the style and layout of web pages. Like HTML and JavaScript, CSS is also a front-end technology. The difference is that HTML is used to structure web page content, JavaScript is used to dynamically interact with web pages, and CSS is used to control the visual effects and layout of web pages.

The development history of CSS can be traced back to the 1990s. At that time, the layout and style of the website were written directly in HTML tags, which made the content and style of the web page mixed together and difficult to maintain and modify. To solve this problem, the W3C (World Wide Web Consortium) released the first CSS specification in 1996, allowing style and layout to be managed independently of HTML.

The main functions of CSS include modifying the color, font, size, spacing, border, background and other styles of web page elements, as well as specifying the position, size, alignment and other layouts of web page elements. CSS can diversify the visual effects and layout of web pages, and enhance the readability, maintainability and accessibility of web pages.

The syntax of CSS is relatively simple and mainly consists of three parts: selector, attribute and attribute value. The selector is used to select the web page element to be modified, the attribute is used to define the style and layout of the element, and the attribute value is used to specify the value of the attribute. Common selectors include label selectors, class selectors, ID selectors, pseudo-class selectors, etc. Commonly used attributes include font, color, background, margin, padding, width, height, position, etc.

In addition to basic CSS syntax, there are also some advanced techniques and applications. For example, CSS box model, cascading and inheritance, floating and clearing, responsive layout, etc. The box model is used to describe the borders, padding and margins of web page elements, cascading and inheritance are used to describe the priority and inheritance characteristics of CSS styles, floating and clearing are used to realize the flow and positioning of web page elements, and responsive layout uses Web page layout adapted to different device sizes and resolutions.

With the development of the Internet, CSS is constantly updated and evolved. Currently, the latest CSS version is CSS3, which includes many new features and modules, such as Flexbox layout, Grid layout, transformation, animation, transition, filtering, gradient, multi-column layout, etc. These new features provide more possibilities for the realization of web page layout and visual effects, and also make front-end development more flexible and easier to operate.

In short, CSS is an essential part of front-end development. It gives web pages unique visual effects and layout, making the website more beautiful, easy to read, and easy to use. With the continuous advancement of technology and the continuous expansion of applications, CSS will continue to develop, bringing more imagination and innovation power to front-end development.

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