Dave Jones' side showed the determination that has taken within sight of the play-off places, and their on-loan midfielder Jason Koumas was one of the only performances to brighten Bramall Lane.
The visitors were led by skipper Darren Purse in defence, his efforts helping to keep the league leaders at bay.
Purse had to be at his best early on as the Blades started the brighter of the two sides but did not fashion openings from their possession.
Nick Montgomery was willing to try his luck from long distance but his shot early on was blocked and a volley later in the first half lacked accuracy.
Steven Kabba, recalled after resting in midweek for the Carling Cup defeat by Reading, almost created the first clear opportunity when he trapped David Unsworth's long pass before driving into the area and pulling the ball back just behind Neil Shipperley.
But the opening exchanges lacked cohesion and composure, illustrated by Rob Kozluk's sliced long-range shot after eight minutes which drifted for a throw-in.
The visitors sensed a chance to get themselves in the game and looked to counter-attack, encouraged by Koumas' free-kick which went over the bar from a promising position.
Cameron Jerome provided their attacking outlet and after 21 minutes was on the end of a Koumas pass taking towards goal. The England Under-21 checked back on to his right foot, giving Phil Jagielka enough time to clear the danger.
The hosts responded by attacking in the next move, with shouts for a penalty after Purse slid to block Montgomery's shot from 20 yards.
Leigh Bromby had the hosts' best chance of the half, although he seemed stunned when Alan Quinn's corner five minutes before the break found him free. The ball trickled towards the goal but Cardiff goalkeeper Neil Alexander managed to scramble clear.
Jeff Whitley forced the first real save of the match, in first-half injury time, when Kevin Cooper pulled back a deep cross from the left. Whitley, the Northern Ireland international, had time on the ball but his rushed shot lacked power and Paddy Kenny saved.
Jerome should have opened the scoring after 49 minutes when Koumas played him through with a measured pass. The Huddersfield-born striker tried to chip Kenny but his effort failed to clear the goalkeeper.
Montgomery had an equally good chance a minute later when Kabba bundled the ball his way, but the midfielder's first effort was saved by Alexander and the second went over the bar.
Blades boss Neil Warnock responded by bringing on Paul Ifill for Keith Gillespie just after the hour mark, but the substitute had similar difficulty creating chances on the right flank.
Danny Webber was brought on with 17 minutes left and the hosts looked to snatch a winner. However, they were limited to just a tame penalty appeal when Kabba's shot was blocked, while Jerome almost got on the end of a flick from substitute Alan Lee.
Koumas forced Kenny into a save in injury time with a free-kick, with Cardiff players appealing for a penalty from the rebound.