The extraordinary measures taken by University of Colorado officials to stop a large, annual pro-marijuana smoke-up on campus half failed, as hundreds of protesters still breached the campus' closed borders and lit up in unison on a field outside a physics lab at 4:20 p.m. But the university succeeded in keeping the protesters off Norlin Quad, the centerpiece of campus where the gathering normally takes place. And the crowd for the event this year stayed small, several hundred participants and onlookers, instead of the 10,000 or more who have joined in the event in the past and smothered the area with marijuana smoke.