CSS Selector Priority: Resolving Style Clashes

In a web application, multiple CSS selectors can apply to an element, potentially leading to style conflicts. Understanding selector priority is crucial for resolving these conflicts effectively.

According to the CSS specification, the following rules determine which selector's styles take precedence:

1. !important Declarations and Inline Styles:
Declarations marked with "!important" and styles defined inline have the highest priority and override all other rules.

2. Specificity:
If no !important declarations or inline styles are present, the specificity of the selector determines its priority. Specificity is calculated based on the number of different elements, classes, and IDs in the selector. A selector with more specific elements takes precedence.

3. Declaration Order:
If multiple selectors have the same specificity, the style rule declared last in the CSS document will be applied. This is because browsers read the CSS file from top to bottom and apply the most recently defined styles.

Example:

p {
  color: red; /* Rule 1 */
}

#main p {
  color: blue; /* Rule 2, more specific than Rule 1 */
}

In this example, an element with the "p" tag will have its color set to blue, regardless of whether it is nested within an element with the "main" ID. This is because Rule 2 has a higher specificity (combines tagname and ID) and was declared after Rule 1.