Reading missed the chance to close the gap on Coca-cola Championship leaders Wolves when they went down to a 2-0 defeat at Swansea.
The Royals started the match just four points adrift of Mick McCarthy's team but the Swans took a deserved lead on the stroke of half-time. The ball came through to Jason Scotland who turned on the edge of the box and slotted a shot past Royals keeper Adam Federici.
Reading were then reduced to 10 men when Liam Rosenior was sent off for a second yellow card when he pulled Nathan Dyer's shirt. The Swans sealed victory when Scotland capitalised on a long ball and played in Andrea Orlandi who sidefooted home.
Third-placed Birmingham entered the match with Cardiff, who started fifth, with just one win in the last four league games.
It was the Bluebirds who took a deserved lead when Joe Ledley scored with half an hour remaining with a drilled, left-footed shot after a cross by Chris Burke found him on the penalty spot.
Blues were poor in the second half and offered little as an attacking force, but they claimed an improbable equaliser when new loan signing Lee Bowyer thumped the ball into the top corner in the last minute.
Sheffield United overcame the loss of top scorer James Beattie with a 2-0 win at Watford. The Blades had dominated the first half but did not take the lead until the 53rd minute when Nick Montgomery's header found Danny Webber unmarked and the forward smashed the ball home.
Darius Henderson doubled the lead after Greg Halford headed the ball down and found the former Watford man in space to hook it into the net after 67 minutes.
The victory sees United regain fourth spot after being temporarily deposed by Preston who were 2-1 winners over Burnley in the lunchtime kick-off.
Substitute Neil Mellor's 85th-minute penalty gave in-form North End victory after a handball by Clarets skipper Steven Caldwell. Callum Davidson had put Preston ahead from the spot in the 53rd minute before Burnley substitute Robbie Blake's stunning free-kick drew his side level in the 77th minute.
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