Which language is utilized by XHTML to format a page's appearance in a Web browser?

XHTML uses Hypertext Markup Language (HTML) to structure content on the web, but it is specifically an extension of HTML designed to be more rigorous and compliant with XML standards. When it comes to the appearance of a webpage in a web browser, however, XHTML itself doesn't handle styling or visual presentation; instead, it relies on Cascading Style Sheets (CSS) to define how the content looks. CSS allows developers to apply styles such as colors, fonts, and layouts, separated from the HTML structure.

In this context, while XHTML defines the markup and structure, it is not directly responsible for formatting — that role belongs to CSS. Therefore, knowing that CSS is the standard method for formatting web pages helps clarify the importance of properly using each technology in web development.