what is css style cascading

css style cascade is a language used to describe the appearance and layout of elements on a web page. Its principles are based on the specificity and priority of selectors. Selector specificity refers to the specificity and priority of the selector. Weight is used to determine the priority of the selector. Generally speaking, the higher the specificity of the selector, the higher the priority. Style cascading determines the styles ultimately applied to elements. By understanding the specificity and priority of selectors, the order of style rules, the origin of style rules, and the importance of style attributes, you can better control and manage the appearance and layout of your web pages. .

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

CSS (Cascading Style Sheets) is a language used to describe the appearance and layout of elements on a web page. In CSS, style cascading means that when multiple style rules are applied to the same element at the same time, certain rules are used to determine the final applied style.

In CSS, style rules consist of selectors and declaration blocks. The selector is used to select the element to be styled, and the declaration block contains a series of properties and values ​​that describe the appearance and layout of the element. Style cascading occurs when multiple style rules are applied to an element at the same time.

The principle of style cascading is based on the specificity and priority of the selector. The specificity of a selector refers to the specificity and weight of the selector, which is used to determine the priority of the selector. Generally speaking, the more specific a selector is, the higher its priority. For example, ID selectors are more specific than class selectors, and class selectors are more specific than element selectors.

In style cascading, if two or more style rules have the same specificity and priority, the final applied style will be determined based on the order of the style rules. Later style rules will override previous style rules. This is the basic principle of style cascading.

In addition to the specificity and priority of the selector, there are some other factors that can affect style cascading. One important factor is the source of the style rules. In CSS, style rules can come from multiple sources, such as external style sheets, internal style sheets, and inline styles. When multiple style rules have the same specificity, precedence, and order, style rules from external style sheets override style rules from internal style sheets and inline styles.

Another factor that affects style cascading is the importance of style attributes. In CSS, there are some style properties that are considered important and override other style properties. These important style attributes can be marked by adding the !important keyword before the attribute value. When multiple style rules have the same specificity, priority, order, and origin, the style rule with the !important keyword overrides the other style rules.

In general, style cascading is an important concept in CSS, which determines the style that is ultimately applied to an element. By understanding the specificity and priority of selectors, the order of style rules, the origin of style rules, and the importance of style attributes, we can better control and manage the appearance and layout of web pages. As a front-end programmer, it is very important to master the principles and rules of style cascading, which can help us write more flexible and maintainable CSS code.

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