What\'s the Difference Between `#` (ID) and `.` (Class) Selectors in CSS?

Understanding the Distinction Between "." and "#" in CSS Style Declarations

When defining styles for elements in CSS, the use of "#" and "." selectors raises questions about their differences and appropriate applications. This article delves into the semantics of these selectors and their impact on style declarations.

Difference Between "#" and "." Selectors

The "#" selector, also known as an id selector, targets a specific element that possesses a unique "id" attribute. In contrast, the "." selector, or class selector, applies styles to multiple elements that share the same "class" attribute. An element can possess multiple classes separated by spaces.

Practical Applications

Typically, "#" is employed to style elements that appear only once, such as layout elements like sidebars or banners. On the other hand, classes are used for repetitive styles. For instance, to create a specialized error message header, one could define a style rule like "h1.error {}" targeting elements with the "error" class.

Specificity Considerations

Selectors also differ in their level of specificity. Id selectors are inherently more specific than class selectors. Consequently, if conflicting styles are defined for the same element, rules defined using the more specific selector (#) will override those defined using the less specific selector (.).

Conclusion

Understanding the distinction between "#" and "." selectors is crucial for effective CSS usage. By discerning when to employ each selector type, developers can achieve precise and tailored styling, with the higher specificity of id selectors ensuring desired styles are applied consistently.

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