Why Do Class and Pseudo-class CSS Selectors Override Pseudo-class-Only Selectors on Hover?

Why CSS Selectors with Higher Specificity Override Others: The Case of Link Appearance on Hover

Introduction

In CSS, when multiple selectors apply to the same element, the one with the highest specificity takes precedence. This principle is evident in the example below, where a selector using both the class and pseudo-class (.foo a:link) overrides other selectors that use only pseudo-classes (e.g., a:hover).

Understanding Specificity

To determine which selector has the highest specificity, consider the following metrics:

• Inline style has the highest specificity (1)
• Id selector has higher specificity than class, element, or universal selector (0)
• Class, element, or universal selector has the same specificity (1)

Explanation of the Example

In the given HTML and CSS code, the following selectors are applied to the link element within the .foo div:

• .foo a:link, .foo a:visited (higher specificity: class and pseudo-class)
• a:link, a:visited (lower specificity: only pseudo-class)
• a:hover, a:active (same specificity as .foo a:link)

Based on the specificity table provided, .foo a:link overrides a:hover because the former has higher precedence due to its inclusion of a class.

Fixing the Issue

To rectify the issue and make hovered links appear red, it is necessary to modify the .foo a:link selector to ensure it does not override the styles defined in a:hover. One possible fix is to add a more specific selector for hover within the .foo context:

.foo a:hover, .foo a:active {
    color: red;
}

By introducing a more specific selector, it takes precedence over the less specific .foo a:link selector, allowing the hover behavior to display the correct color.

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