How is a CSS class declared in a stylesheet?

A CSS class is declared in a stylesheet by using a dot (.) followed by the class name. This syntax is a fundamental aspect of CSS, allowing developers to define styles that can be applied to multiple elements throughout an HTML document.

When you see a class declaration like .classname { property: value; }, it indicates that any HTML element with the class attribute set to classname will receive the specified styles. This provides a powerful way to maintain consistency and manage the look of a website by applying reusable style rules across various elements.

The other symbols mentioned do not correctly denote a CSS class. The hash symbol (#) is used for IDs, which target a single unique element, an asterisk (*) is often associated with universal selectors or wildcard selectors in CSS, and a colon (:) is used in pseudo-classes and pseudo-elements to style elements based on their state or position in the document tree. Understanding the correct syntax for CSS classes is essential for effective website styling and design.