Teenagers are often inadvertently exposed to porn when they conduct unrelated Web searches, said Patricia Greenfield, a psychology professor and director of UCLA's Children's Digital Media Center.
In a 1998 study, nearly half of students in grades three through eight reported visiting Web sites with adult content.
That figure is probably higher today, Greenfield said. Greenfield recommends keeping lines of communication open with children, and surfing the Internet with young children.
In chat rooms, the youth are sexually pursued, the study found.
Separate research detailed the extent to which teens seek advice on sex and relationships from anonymous peers on the Web -- and the ways they keep parents out of the loop.
Speaking in coded language has been used for years by teenagers trying to hide something, or communicating in their own way.