Advertisements placed on media websites are more trusted than those on social-media sites and general web portals, says a study by the Online Publishers Association and Harris Interactive.

The online survey of more than 2,900 people sought to understand why consumers respond to ads on the web differently depending on the content environment.

It showed that media sites - such as those of newspaper and magazines - offered advertisers greater "halo effect" for their messages.

The survey found that consumers are more likely to trust content on media sites (72 per cent) than general web portals (60 per cent) and social media (23 per cent).

Also, audiences are more likely to believe that advertisers on media sites are high quality and reputable (24 per cent), compared to portal channels (20 per cent) and social media (8 per cent).

The study concluded that consumers perceive and act differently depending on where the ad appears.