css priority setting

In web development, CSS style is an important element of web page beautification. It can make web pages more beautiful and easier to read by setting colors, fonts, layout, etc. However, when the same element is defined by multiple CSS rules, CSS priority issues arise. So, how to set CSS priority correctly?

CSS priority refers to which rule has a higher priority among multiple CSS rules, thereby determining which style to apply. Here are the priorities of CSS rules, from highest to lowest:

1. !important

!important is the highest priority declaration in CSS, which overrides all other CSS rule. But use !important with caution and only when you really need to override other rules.

For example:

.color {
  color: red !important;
}

2. Inline style

Inline style refers to defining the CSS style directly in the HTML tag, and its priority is second to !important.

For example:

<h1 style="color: blue;">Hello World!</h1>

3. ID selector

The ID selector defines the style based on the id attribute of the HTML element, and its priority is higher than the class Selector and label selector high.

For example:

#header {
  background-color: gray;
}

4. Class selector, attribute selector and pseudo-class

The class selector defines the style based on the class attribute of the HTML element , has a higher priority than the label selector.

Attribute selectors define styles based on the attributes of HTML elements, such as [type="text"].

Pseudo-classes define styles through the state of HTML elements, such as: hover.

For example:

p.intro {
  font-size: 16px;
}

input[type="text"] {
  border: 1px solid gray;
}

a:hover {
  color: green;
}

5. Tag selector and pseudo-element

The tag selector defines the style based on the tag name of the HTML element, which is the most Commonly used selectors.

Pseudo elements are styled through special characters in HTML elements, such as ::before and ::after.

For example:

h1 {
  font-size: 24px;
}

li::before {
  content: "-";
}

In actual development, it is recommended to avoid using !important because it may break the expectations of CSS rules and cause confusion. Tag selectors should be used in preference to class selectors, ID selectors, and other selectors only when necessary.

When determining the discount level, you also need to understand the cascading order of CSS rules. When two CSS rules with the same priority are applied to the same element, the cascading order will determine which rule should be applied. The cascading order is determined by the type of element (HTML element, pseudo-element), the source of the rule (associative style sheet, user style sheet, proxy style sheet) and the specificity of the CSS rule.

In short, CSS priority setting is an indispensable part of web page beautification. Correct settings can make web pages more beautiful and improve user experience.

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