A social bookmarking service is a centralized online service which enables users to add, annotate, edit, and share bookmarks of web documents. Social bookmarking is a user-defined taxonomy system for bookmark s. Such taxonomy is sometimes called a folksonomy and the bookmarks are referred to as tags. Tagging is a significant feature of social bookmarking systems, enabling users to organize their bookmarks in flexible ways and develop shared vocabularies known as folksonomies. Unlike storing bookmarks in a folder on your computer, tagged pages are stored on the Web and can be accessed from any computer. Technorati, a blogging site, describes the system as “The real-time Web, organized by you.” Web sites dedicated to social bookmarking, such as Flickr and del.icio.us, provide users with a place to store, categorize, annotate and share favorite Web pages and files.