Browsing the web involves two main tasks: finding the right web page and then making sense of its content. A significant amount of research has gone into supporting the task of finding web resources through 'standard' information retrieval mechanisms, or semantics-enhanced search. Much less attention has been paid to the second problem. In this paper we describe Magpie, a tool which supports the interpretation of web pages. Magpie acts as a complementary knowledge source, which a reader can call upon to quickly gain access to any background knowledge relevant to a web resource. Magpie works by automatically associating an ontology based semantic layer to web resources, allowing relevant services to be directly invoked within a standard web browser. The functionality of Magpie is illustrated using examples of how it has been integrated with our lab's web resources.