Cascading Style Sheets (CSS) are a markup language used to design and format HTML documents. CSS allows es to define the appearance of a web page, such as colors, fonts, spacing, and positioning of elements.
CSS files have indirect SEO relevance, as they enable the separation of content and presentation. Search engines prefer well-structured, easily accessible code. By using CSS, developers can keep the HTML code cleaner and provide an improved user experience, which can have a positive impact on SEO ratings. In addition, CSS enables better adaptation and optimization of the website for different devices and screen sizes, which can also influence SEO performance.