what is css cascading

CSS cascading "Cascading Style Sheets" means that when multiple CSS style rules are applied to the same HTML element at the same time, the final applied style is determined based on certain priorities and rules. When multiple rule selectors are used at the same time When an element is matched, cascading will occur. Through CSS cascading, developers can easily control and adjust the appearance and layout of web pages to achieve flexible combination and inheritance of styles.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

CSS cascading (Cascading Style Sheets, CSS for short) refers to when multiple CSS style rules are applied to the same HTML element at the same time, the final applied style is determined based on certain priorities and rules. Cascading occurs when multiple rule selectors match an element at the same time.

The principle of CSS cascading is based on the following factors:

1. Priority: Each CSS rule has a priority that is used to determine which rule has Higher weight. Priority is generally determined by the selector's specificity, position, and !important declaration. For example, rules using ID selectors have higher priority, while rules using universal selectors have lower priority.

2. Specificity: Specificity is a value that measures the weight of a selector and is used to determine which rule is more specific. The specificity of a selector is determined by the number and type of its components (tag name, class selector, ID selector, etc.). The higher the specificity value, the higher the priority.

3. Source order: If multiple rules have the same priority and specificity, the last defined rule will override the previous rule. This means that later rules in the style sheet will be layered on top of earlier rules.

When applying CSS styles, the browser will decide which style rule to use based on these factors. If there is a conflict, the browser will resolve the conflict based on rules such as priority, specificity, and declaration order, and determine the final style to be applied.

Through CSS cascading, developers can easily control and adjust the appearance and layout of web pages to achieve flexible combination and inheritance of styles. This makes CSS a powerful and flexible styling language.

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