13. A method comprising: receiving at a client terminal from a network server, ratings in respect of Uniform Resource Identifiers; caching the received ratings at the client terminal within a client cache; and for a Uniform Resource Identifier identified at the client terminal for which a rating is required, 1) identifying a plurality of separate components of the Uniform Resource Identifier, 2) querying the client cache to determine whether or not it contains a rating for a Uniform Resource Identifier matching query string, the query string being a first component of the identified Uniform Resource Identifier, and whether a further query is required to the cache or to an external server, 3) if a further query is required to the cache, repeating step 2) for one or more iterations, extending the query string with a further component until either no further query is required, or a query is required to the external server; 4) if a further query is required to the external server, extending the query string with a further component and sending a query to the server, receiving a response indicating a rating for the query string or that no rating exists, and indicating whether or not a further query is required; 5) if a further query is required in step 4), repeating step 4) for one or more iterations, extending the query string with a further component until either no further query is required or there are no further components.
13. A method comprising: receiving at a client terminal from a network server, ratings in respect of Uniform Resource Identifiers; caching the received ratings at the client terminal within a client cache; and for a Uniform Resource Identifier identified at the client terminal for which a rating is required, 1) identifying a plurality of separate components of the Uniform Resource Identifier, 2) querying the client cache to determine whether or not it contains a rating for a Uniform Resource Identifier matching query string, the query string being a first component of the identified Uniform Resource Identifier, and whether a further query is required to the cache or to an external server, 3) if a further query is required to the cache, repeating step 2) for one or more iterations, extending the query string with a further component until either no further query is required, or a query is required to the external server; 4) if a further query is required to the external server, extending the query string with a further component and sending a query to the server, receiving a response indicating a rating for the query string or that no rating exists, and indicating whether or not a further query is required; 5) if a further query is required in step 4), repeating step 4) for one or more iterations, extending the query string with a further component until either no further query is required or there are no further components. 16. A method according to claim 13 , wherein a query sent to the rating server contains the complete identified Uniform Resource Identifier.