What is the purpose of CSS in web design?

CSS, or Cascading Style Sheets, is primarily used to dictate the visual presentation of HTML elements on a webpage. It allows designers and developers to separate the content of their web pages from the design aspects. This means that while HTML structures the content, CSS determines how that content looks, including aspects such as colors, fonts, layouts, spacing, and overall visual aesthetics.

The power of CSS lies in its ability to apply styles consistently across multiple pages, making it easy to maintain a coherent look and feel throughout an entire website. This separation of structure (HTML) and style (CSS) enhances both flexibility and manageability, allowing for simpler updates to the design without altering the underlying content.

In contrast, other choices relate to aspects not defined by CSS. For instance, creating webpage structure is the role of HTML, whereas managing web browsers pertains to how browsers interpret and display web content, which is not a function of CSS. Finally, storing web data is a task associated with databases and servers, not with CSS's purpose in web design.