The World Wide Web (commonly shortened to the Web) is a system of interlinked, hypertext documents accessed via the Internet. With a web browser, a user views web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks. The World Wide Web was created in 1989 by Sir Tim Berners-Lee and Sir Sam Walker from the United Kingdom, and Robert Cailliau from Belgium, working at CERN in Geneva, Switzerland. Since then, Berners-Lee has played an active role in guiding the development of web standards (such as the markup languages in which web pages are composed), and in recent years has advocated his vision of a Semantic Web.