New Brighton boss Steve Coppell kicked off his reign with an extraordinary 11th league defeat on the trot for the Seagulls.
The rock-bottom South Coast club stunned promotion chasing Sheffield United by taking a 2-0 lead at half time, but a late hat-trick by substitute Carl Asaba, including a couple of penalties, gave the Blades an amazing seventh win out of nine in all competitions.
Coppell could hardly have wished for a more encouraging start in the opening 45 minutes. Gary Hart gave Brighton a 23rd minute lead with a diving header from a Graham Barrett cross.
Irishman Barrett, on loan from Arsenal, headed home his first goal for the club 11 minutes later from a centre by captain Bobby Zamora.
Brighton's Dutch goalkeeper Michels Kuipers had twice made fine saves from Wayne Allison in the first 20 minutes and his team seemed on course for their second win of the season until Asaba's introduction.
The former Gillingham marksman came on in the 59th minute in place of Michael Boulding. He almost halved United's arrears immediately before Michael Brown brought them back into the match after 70 minutes with a low shot from 20 yards.
Asaba knocked in the equaliser from close range after 78 minutes following a superb solo run into the box by teenager Michael Tonge.
Referee Phil Prosser controversially ruled that Kuipers brought down Asaba in the area after 86 minutes. Asaba scored from the resulting spot kick and did so again after 88 minutes when Adam Virgo pushed over Allison.
Brighton fans, infuriated by Prosser's decisions, left their seats and gathered on the running track around the Withdean pitch to protest. Police and stewards had to move in to prevent the threat of a pitch invasion