When encountering problems such that the CSS style does not take effect, is overwritten or inheritance confusing, the CSS feature value and inheritance mechanism should be given priority. 1. Understand and calculate the specific weight of the selector, inline style > ID selector > Class selector, attribute selector, pseudo-class > element selector and pseudo-element. Rules with high weights will override the rules with low weights, even if the latter appears in the code; you can view the style source and weights through the "Computed" panel of the browser developer tool. 2. Avoid abuse!important, only used when overwriting third-party library styles or emergency repairs. It is also recommended to optimize the structure by increasing the selector weight, splitting the class, or adopting BEM naming specifications. 3. Pay attention to whether the attributes are inheritable. For example, color and font-size will inherit, while border and margin will not. You can confirm the source of the attribute through the Computed tag and use inherit, initial or unset to control the inheritance behavior. 4. Use the cascading order to manage style priorities, including style source, !important, rule order and other factors. Note that the CSS file loading order will affect the cascading order. You can use the developer tools to view the specific style source, or use @layer to control the cascading order to avoid style conflicts.

When encountering the problem that the CSS style does not take effect, is overwritten, or the inheritance relationship is confusing, many people's first reaction is "Is the selector written incorrectly?" In fact, it is often the CSS characteristics and inheritance at work. To solve these problems, the key is to understand their working mechanisms and learn to check and adjust.

1. Understand the priority of CSS attribute values

The "weight" of different selectors in CSS determines which style will eventually be applied to the element. This weight is specific. It is not a simple "who is behind and who takes effect", but there is a set of calculation rules:

• The inline style has the highest weight (such as style="color: red" )
• ID selector (such as #header )
• Class selector, attribute selector, pseudo-class (such as .btn , [type="text"] , :hover ) again
• Element selectors and pseudo-elements (such as div , ::before ) are weakest

For example:

 /* Weight: 0,1,0 */
#main {
  color: red;
}

/* Weight: 0,0,3 */
div.container .text {
  color: blue;
}

Although .text appears behind, the color is still red because #main has a higher weight.

Debugging suggestions:

• Open the browser developer tool, select the target element, and view what styles are applied in the "Computed" panel.
• Tools usually display the specific weight of each rule and mark the overridden style (usually crossed out state).
• If you find that a style is not effective, first check whether its selector is overwritten by a higher-weighted selector.

2. Avoid abuse!important

Some developers directly add !important when they see that the style does not take effect. Although this can solve the problem, it will cause maintenance troubles, especially when multiple people collaborate, it is easy to cause confusion.

When can it be used?

• Third-party library style overlay (such as some UI frameworks)
• Quickly fix emergency online problems (remember to follow-up optimization)

More recommended practices:

• Increase the weight of the selector, such as changing from .btn .container .btn
• Split the style into a separate class to avoid too deep nesting
• Use BEM or similar naming specifications to improve maintainability

3. Pay attention to the influence of inheritance and default styles

Not all CSS properties are automatically inherited. For example, color and font-size will inherit, while border and margin will not. If you find an element "inexplicably" with a font size or color, it is likely that it is inherited from the parent.

Common phenomena:

• Set p { font-size: 16px } , but it actually shows that it is larger or smaller - maybe the parent container has a larger font size and is inherited
• Text colors in custom components are always inconsistent with expectations - maybe inherited from global themes

Debugging suggestions:

• Check the attribute source in the "Computed" tab to confirm whether it comes from inheritance
• Use inherit to explicitly control inheritance behavior (e.g. color: inherit )
• Quickly reset properties with initial or unset for testing

4. Manage style priority using cascading order

In addition to specificity, CSS also determines which rule takes effect through cascade. The order of stacking is determined by the following factors:

• Style source (user agent style, user style, author style)
• Is it used !important
• The order in which the rules appear (the latter wins under the same weight)

This means:

• When multiple CSS files are introduced, the rules of the same name in the subsequently loaded file may overwrite the previous one.
• In the style sheet introduced using <link> , those with the order are backwards and have a higher stacking order (provided that the specificity is the same)

Debugging suggestions:

• View the file and line number of the specific style source in the developer tool
• Unify the CSS loading order to avoid logical confusion
• @layer (supported by modern browsers) can be used appropriately to control the cascade order for key styles

Basically that's it. These questions may seem simple, but are easily overlooked in large projects. Master the basic principles of specificity and inheritance, and cooperate with browser tools, you can quickly locate and fix style conflicts.

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