Three-quarters of 16 and 17 year-olds have been exposed accidentally to pornographic websites on the Internet, and two in five boys have found them deliberately, according to the Australia Institute report released on Monday. The material these teenagers are seeing is often violent and extreme, and there is evidence that regular exposure is damaging their attitudes and relationships. Rape, bestiality and bondage cannot be shown in "adult" videos and magazines, but any child can find these images on the Internet.