Film certification-style ratings are coming to the internet, as the result of a link-up between the British Board of Film Classification and an internet service provider. The ISP, Tibboh, is using the BBFC classification system – which rates films as U, PG, 12, 15 or 18 – and applying it to websites. Around 3bn sites have already been rated, with more set to follow.

Tibboh employs the Netsweeper system already in use in schools to determine each site's suitability for different age groups, and the firm has said it will take note of public suggestions for ratings. Using a USB dongle developed by Tibboh, parents will be able to filter out all content rated as older than they deem suitable. However, the service does not come free: there is a monthly charge of £19.99 for the service, which is available from Amazon and from Tibboh's own website.

Among the decisions already made are to rate social networking sites such as Facebook and Twitter as 12-certificate, in line with guidance from the sites themselves. Guardian.co.uk has been rated U. It is not known whether a "contains mild liberalism" warning has been attached.