It was Arsenal who snatched the place in the fifth round as substitute Theo Walcott had a volley deflected into the corner with five minutes on the clock.
Read how it all unfolded in our minute-by-minute live coverage below.
2.01pmAfternoon folks! This match has all the ingredients to be a cup classic. It's a beautiful day on the south coast, which has avoided much of the heavy snow to hit the country overnight. Conditions are perfect at the Amex and Arsenal will be delighted with that.
2.13pmWenger has rested five of his usual starting XI then, with Bacary Sagna, Kieran Gibbs, Jack Wilshere, Santi Cazorla and Walcott dropping to the bench. It's still a pretty menacing Gunners lineup, mind. Both Lukas Podolski and Olivier Giroud were on form against West Ham on Wednesday.
2.17pmOne surprise starter for Arsenal is Andre Santos. The Brazilian left-back hasn't been the biggest hit since joining a year and a half ago from Fenerbahce.
2.20pmThere is one fourth round tie already underway and there's about 15 minutes left of Stoke 0-0 Man City. The visitors are doing all the pressing and you can keep up with the final stages with Liam Apicella's live commentary here.
2.23pmThe headline news from Brighton's point of view is that new signing Leonardo Ulloa makes his debut up front. What a game to make your bow, eh?
2.28pmLATE goal for City! It looks like the Premier League champions are going to squeeze through at the expense of Stoke as Pablo Zabaleta steals in at the far post and tucks home with the outside of his boot.
2.32pmThere's eight other 3pm kickoffs in the FA Cup and I'll keep you updated on all the big goals as they go in across the country.
2.37pmLet's take a look at how these two sides are getting on in the league. Brighton sit just outside the Championship's playoff zone in seventh but they're four points adrift of sixth place. Tuesday's late draw at Blackburn meant that Gus Poyet's side became the first in the second tier to reach 12 draws this season. Another level scoreline today would be a dream result for the Seagulls.
2.39pmArsenal, meanwhile, are a disappointing sixth in the Premier League, four points adrift of great rivals Tottenham Hotspur in that crucial fourth place.
2.41pmFULL-TIME at the Brittania! City advance to the fifth round thanks to Zabaleta's calm finish five minutes from time. Click here to read Sian Cowper's match report.
2.44pmThere's some comical scenes outside the Britannia as the home fans trudge their way home in the snow. One of them might get on You've Been Framed if they really go for it.
2.48pmPREDICTION TIME! Back to our feature game and it's time for me to say exactly what the result won't be! I'm going for a narrow win for the Gunners, 1-0 to Wenger's men.
2.49pmMan City captain Vincent Kompany left the lunchtime game early with an injury but he's hoping it's not too serious. He's just tweeted this: "On to the next round and a fifth consecutive clean sheet! I hope I won't be out for too long but the team seems to be strong as ever. #FACup"
2.50pmThe warm-ups are all done at the Amex and Brighton really do seem up for this - they had a huddle after the warm-up!
2.55pmFIVE minutes until kickoff. In terms of the key battles this afternoon, will Greer and El-Abd be able to cope with the attacking trio of Podolski, Giroud and Oxlade-Chamberlain?
2.58pmAs I mentioned earlier, it's a packed house at the Amex and here come the players out of the tunnel. Both teams are in their home strips, with Brighton in their blue-and-white horizontal stripes, blue shorts and white socks and Arsenal in red tops, white shorts and red socks. Kickoff imminent.
0 minKICKOFF: Today's referee Michael Oliver gets us underway.
2 minBrighton are expecting a record crowd this afternoon and it's a very noisy atmosphere early on. No action of note on the pitch yet.
4 minAlmost a nervy moment for Brighton stopper Ankergren as he dilly-dallies on the ball under pressure from Giroud.
3.06pmGoalflash! Plenty of early goals in the Cup this afternoon! QPR are behind at home to League One side MK Dons while Wigan lead at Macclesfield and Reading go ahead against Sheffield United.
7 minCalderon knows Podolski is behind him at the back post so bundles it out for Arsenal's first corner. Oxlade-Chamberlain delivers and that's well cleared by the home defence.
10 minPatient passing football from Brighton on the edge of the Arsenal area comes to an end when Bridge's (that's Wayne Bridge) volleyed cross goes over the heads of everyone and out for a goal kick.
12 minYELLOW! The first booking of the game goes to Brighton's David Lopez after a cynical clip of Rosicky's heels.
15 minA quarter of an hour into the game and there really has been nothing significant to report. The Gunners' star front line have produced very little.
16 minTypical, just typical. The moment I say that there has been no action, both sides hit the target. Brighton had a golden chance down one end as Barnes beat the offside trap but was denied by Szczesny. Arsenal broke away from the resulting corner and Giroud shifted on to his left on the edge of the area before smashing into the top corner. Fine finish from the Frenchman.
3.21pmGoal for Everton at the Reebok against Bolton at it's Steven Pienaar who tucks home for the Toffees.
23 minBrighton can certainly play football. More composed passing in the final third is ruined by a naff cross. This time it's right-back Calderon who floats his centre onto the roof of the net.
25 minThe Seagulls have responded well to going behind and they almost score a very clever goal. Barnes flicks the cross from the right into the path of new boy Ulloa but he can't get it under control to shoot from six yards.
3.29pmGoal for Bolton! Everton weren't ahead for long at the Reebok as Marvin Sordell equalises for the Trotters.
30 minDISALLOWED! Ulloa thinks he's made a dream start in Brighton colours as he is presented with the easiest of tap-ins. However, he was offside when Buckley sent the cross in. That chance all came from Santos needlessly trying to take on his man in front of the box.
33 minDear oh dear, that's poor from Arsenal. Brighton are definitely targeting the right-hand side, looking to exploit the unreliable Santos. Buckley wins a corner and the ball in by Lopez is met by an unmarked Barnes, who gets to the ball ahead of Szczesny right in front of goal.
36 minBrighton sub: Unfortunately for the Seagulls, their skipper Gordon Greer has had to go off injured. Gary Dicker comes on in his place.
39 minIt looks as if Dicker is going to play in the centre of midfield, with Lopez moving over to right-back and Calderon joining El-Abd in the middle of the back four.
3.41pmGoalflash! MK Dons look to be pulling off a 'cupset' at QPR as they go 2-0 up at Loftus Road. Another side now two ahead is Reading as Mikele Leigertwood nets against Sheffield United.
44 minHalf time is fast approaching on the south coast and it's Brighton who are in the ascendency. The Championship side have responded really well to that suckerpunch of a goal from Giroud.
45 minThree minutes added on at the end of the first half.
45+1 minBuckley trudges off with an injury but he'll be OK to continue. Santos's half doesn't get any better as he decides to emulate his fellow Brazilian left-back Roberto Carlos by taking a shot on from 40-odd yards. Needless to say the ball didn't bulge the net.
3.50pmWell that one got going after a stale opening quarter of an hour. Arsenal took the lead through a super Giroud finish but were pegged back by Barnes's point-blank header.
3.54pmThere's plenty of other games in the FA Cup, Championship and much more. Click here to see all of today's scores.
3.58pmJust seen a replay of the Giroud goal and it really was a marvellous finish, bent round the defender and in to the top corner. Class.
4.01pmSome breaking news from the Premier League is that Manchester City captain Vincent Kompany has been ruled out for their next game against QPR after picking up an injury at Stoke earlier.
4.05pmBrighton sub:Gus Poyet has made a second change and it's Buckley off for Kazenga Lua Lua. No changes for the Gunners.
4.09pmGoalflash! MK Dons and Reading have both scored at a similar time to go 3-0 up in their respective games. The Dons now lead at QPR while Reading have virtually sealed the points against Sheffield United.
51 minSAVE! Rosicky drives at the Arsenal defence and seems to be brought down. Oliver doesn't give anything but the ball rolls to Jenkinson who lashes goalwards and Ankergren has to beat it away.
54 minOFF THE BAR! The Gunners win a free kick just outside the D and it's Podolski who clips it over the wall. Ankergren doesn't even bother going for it and breathes a sigh of relief as it clatters up and away off the woodwork.
56 minIt's another super finish from Mr Giroud. Diaby clips the ball over the top for the Frenchman and he takes one touch after watching it over his shoulder before finishing bravely on the half-volley right in front of Ankergren.
60 minCHANCE! So close to Giroud's hat-trick. A Brighton attack is hoofed clear by Ramsey and it falls straight to Giroud. He lays it off for Rosicky and then sets off down the pitch. Rosicky picks him out with a raking pass and the Frenchman holds off El-Abd's challenge before volleying at goal, with Ankergren doing well to keep it out.
62 minIt's a debut goal for Leonardo Ulloa! I was just about to say that Arsenal were looking more and more dangerous on the counter but then Brighton equalise once more. Barnes sends over a stunning cross from the right and Ulloa is on hand to thump a diving header low into the net.
74 minGiroud takes it, not Podolski, and he strikes it well. It fizzes over the wall but never had enough dip to get it back under the crossbar.
4.27pmAnother for MK Dons! This is some scoreline for the League One club, they now lead 4-0 at QPR.
78 minWalcott almost sneaks into the area but he's stopped by El Abd.
66 minYELLOW! Ramsey the first Arsenal player to go into the book.
79 minArsenal sub: Wenger makes his final change and it's the awful Santos off for Kieran Gibbs. Seems quite fitting that the Brazilian's last action was to blaze a shot into row Z.
69 minArsenal subs: Theo Walcott is on for Oxlade-Chamberlain while Jack Wilshere takes the place of Rosicky.
4.40pmGoal at Carrow Road and it's not Norwich who are leading! Non-league Luton have taken the lead with 10 minutes left.
82 minPodolski breaks clear down the left and picks out Giroud's clever movement. It's a tough ask for the Frenchman to turn it goalwards and he hits it into the turf and over.
85 minIt's that man Theo again! An Arsenal corner is cleared out to the edge of the area and Walcott sidefoots a volley first time towards goal. It takes a massive deflection off the head of El-Abd, looping into the far corner past a deceived Mackail-Smith on the post.
88 minWhoa! That's blisteringly quick running from Walcott. He outpaces a pair of Brighton defenders and is brought down by El-Abd. He gets up quickly though and the referee plays an advantage for the England international who bears down on goal but sees his shot saved by Ankergren.
5.25pmApologies for the delay towards the end of the match, we suffered technical meltdown. Arsenal are into the fifth round of the FA Cup at Brighton's expense it was a true classic cup tie at the Amex. Thanks for joining Sports Mole for coverage, good evening!