A pair of stadium power outages could not prevent the San Francisco 49ers from overcoming the Pittsburgh Steelers 20-3 on Monday in a gritty matchup between playoff-bound teams.The lights went out at Candlestick Park on two occasions, delaying the game’s start for 20 minutes before again halting the action for about 15 minutes early in the second quarter.The blackouts, however, had little effect on the home side, who controlled the game from start to finish.San Francisco forced Steelers quarterback Ben Roethlisberger, playing through an ankle sprain, into two first-quarter interceptions to limit Pittsburgh’s air attack and take a 6-0 halftime lead.The 49ers squeezed the life out of the Steelers in the second half. Alex Smith tossed a one-yard pass to Vernon Davis for a 13-3 third quarter lead before Frank Gore capped a drive with a five-yard touchdown run with 9:10 left in the contest. San Francisco finished with just 287 total yards but dictated the action to keep pace for a top NFC playoff seed.