As the Internet infiltrates people's lives, it has changed the way businesses operate, stocks are traded and news is dispersed. It also is changing the face of the art world. Standing at the forefront of this change is Mark Amerika, a pioneer in the digital arts field and a University of Colorado at Boulder assistant professor in the fine arts department. Amerika, who last spring was named one of Time magazine's top 100 innovators for the new century, creates his online artwork with computer graphics, music and hypertexts in an ever-changing medium.