Goals from Alex Oxlade-Chamberlain and Lukas Podolski this afternoon were enough for a 2-1 victory that sets the Gunners up a quarter final home tie with Everton next month but it was the former World Cup final referee's decisions that caught most of the attention.
Steven Gerrard scored a consolation a second half penalty for the visitors after Podolski clumsily fouled Luis Suarez in the penalty area, but Webb angered the Anfield club's supporters for not pointing to the spot a second time when Oxlade-Chamberlain clearly bundled Suarez in the area just moments later.
Webb also drew criticism from Arsenal fans for refusing to dismiss Gerrard following a late challenge on Oxlade-Chamberlain which would have earned him a second booking in the game.
It is not the first time the 42-year-old's officiating has courted controversy. He was previously criticised for failing to send off Holland's Nigel de Jong for his kung-fu kick on Spain midfielder Xabi Alonso in the first half of the 2010 World Cup final - a decision he later conceded was an error of judgement.
Liverpool's love-hate relationship with Webb is also well documented. In 2011 he was slammed by then manager Kenny Dalglish for awarding a dubious penalty to Manchester United in the opening minute of an FA Cup clash at Old Trafford that ultimately won the tie for the hosts.
Later in the game he sent off Gerrard for a two-footed challenge on Michael Carrick. Winger Ryan Babel reacted to the manner of his side's defeat by posting a mocked-up picture of the Rotherham official in a United shirt on Twitter, which earned him a £10,000 fine from the Football Association for improper misconduct.
Webb is widely regarded as England's best referee and among the continental elite, having previously oversaw various showpiece occasions, including the the FA Cup and Champions League finals. But his performance at the Emirates Stadium has called that reputation into question once again.
Howard Webb is an absolute disgrace…dreadful referee for both sides. Stone wall penalty missed (thankfully) and no second yellow for Gerrard— Ben Harrison (@RednWhite_Army) February 16, 2014
The FA need to investigate Howard webb there misses a blatent penalty, blatent second yellow for Gerrard booking half the pitch in the first— Jay Edwards (@jayedwards90) February 16, 2014
Howard Webb should've sent off Gerrard, gave a soft pen, and most general decisions went against us!?!? How can people say he was a Gooner?— TheGamerCan / Curt ށ (@CurtisMorton) February 16, 2014
Howard Webb completely bottled that. Gerrard should be off— The Arsenal (@Artekkers) February 16, 2014
— David O'Reilly (@tackleberry11) February 16, 2014
Howard Webb is simply not just a terrible ref but a cowardly one too! Stonwall Penalty and Gerrard tackle later proof of that! shocking #LFC
Howard Webb had control of the game but bottled some decisions. A penalty for #LFC and a red card for Gerrard.— Ify (@Ifynaija) February 16, 2014
10 yards tops, clear vision, clear penalty and nothing. Howard Webb apparently the best. Embarrassing. Lets see some action @FA.— Michael Allan (@Mikey_Allan) February 16, 2014
image: © Ronnie Macdonald