A content delivery server configured to select from multiple content items a set of content items for display to a user at a user terminal, the content delivery server having access to content identifiers, identifying content items for delivery; a processor operating a content selection program which is arranged to receive the context data for different contexts and to select a set of content items in dependence on the context data, wherein the content items in the set vary with the context data, such that the content of items in a first set for a user in a first context are different from the content of items in a second set for the same user in a second context, and to transmit a recommendation message to the user terminal comprising a set of content identifiers.