Lewis beat Martyn Margetson to the ball at the edge of the 6 yard box after Paul Brooker had put in a left sided decent cross which caught all the Town defenders ball-watching.
It was unfair on the Welsh 'keeper who had already stopped efforts from Brooker and Simon Morgan, and kept out the ever-dangerous Bobby Zamora with a point blank double save just before half time.
It was a rare mistake from the Welshman, who also made a save off Lewis' knees during the second half and had to contend with an increasingly bobbly pitch - Paul Watson had Margetson scrambling for the ball at the second attempt due to the poor condition of the narrow pitch.
Conditions at the compact Withdean Stadium combined with the long ball game employed by the Seagulls made chances few and far between for both sides.
The Terriers had effectively contained the Seagulls during the match and, other than the unfortunate goal, didn't look like conceding with midfielders tracking back where necessary.
They did, however, lack a cutting edge with Chris Hay and Kenny Irons coming close but not close enough.
Town's best chance came through Leon Knight who made a superb late run in the 64th minute but failed to connect fully with a Hay cross which would have levelled the scores.
Knight made a nuisance of himself along with Danny Schofield but there was just too little room in which to fully employ the passing game which Town tried to play.
The withdrawl of Clyde Wijnhard made things more difficult in the second half as the Terriers struggled without an obvious target-man.
Towards the end the home side were under intense pressure from the Terriers but their defence could not be breached.
Read Mel Booth's match report in the Examiner on Monday. Have your say in the Message board below. Selected comments may be published in the Examiner.
Brighton (4-4-2): Kuipers, Pethick, Cullip, Morgan, Watson, Melton, Carpenter, Lewis, Hart, Zamora, Brooker
Subs not used: Mayo, Rogers, Jones, Lee, Webb
Scorer: Lewis 53
Town (4-4-2): Margetson, Jenkins, Evans, Gray, Clarke, Hay, Heary, Holland, Schofield, Knight, Wijnhard (Irons 68)
Subs not used: Irons, Dyson, Macari, Mattis, P. Senior
Referee: Steve Bennett (Kent)
Match points follow on subsequent pages
94 mins: Zamora was forward on the counter-attack as Brighton finally got the ball and laid seige to the Town goal.
93 mins: Heary hit the ball long. Knight fell over in the area but didn't get the penalty.
92 mins: Town were piling the pressure on in a late effort to get the equaliser.
91 mins: There were 4 minutes of added time for Town to get the equaliser.
90 mins: Schofield's long ball to Knight was crossed brilliantly in front of Kuiper's goal. The Dutch 'keeper was beaten but nobody was there to convert!
89 mins: Zamora left the ball and Gray cleared before another Brighton player could strike. Gray hit another great clearing header.
88 mins: Schofield was put off by Morgan as he tried to receive a direct ball. Cullip cleared after Schofield couldn't retain control of the ball.
86 mins: Schofield went past 3 defenders but couldn't make it past Junior Lewis.
85 mins: Gray made a great tackle on Zamora but was penalised for tugging the Brighton striker's shirt. Margetson saved off Lewis' knees with Brooker surging in.
83 mins: Lou Macari made another tactical change and switched Hay and Knight.
81 mins: Clarke's cross was punched out by Kuipers and a melee ensued from which Heary belted wayward.
80 mins: Kuipers collected from Evans under pressure from Schofield.
79 mins: Irons' corner was picked up by Holland as Town tried to force the equaliser.
76 mins: Watson's cross drew a glancing header from which Margetson collected at the second attempt after the loose ball nearly crossed the line off a bobble.
72 mins: Jenkins crossed for Schofield but he didn't get a good contact.
71 mins: Brooker's shot was deflected away for a corner by Kevin Gray.
69 mins: Knight's turn and cross was too high for Chris Hay. Town were keeping the ball well but were lacking a cutting edge in this tense encounter.
67 mins: Clyde Wijnhard was being withdrawn for Kenny Irons. Town re-shuffled with Schofield going up front and Holland stepping out wide to the left. The Dutchman looked puzzled and disappointed as he trudged off.
66 mins: Carpenter pushed the ball past Clarke and then ran into him to attempt for a foul claim.
64 mins: Hay pressurised the defenders with help from Wijnhard and put a cross in which was perfect for Leon Knight who skimmed the ball just wide. Knight then ran into the 'keeper and both went down injured.
63 mins: Chris Hay hit the ball over the bar with his left boot after a great ball for Wijnhard was laid off by the Dutchman.
63 mins: Kenny Irons was warming up as Schofield tried to get past Lewis.
62 mins: Jenkins' effort was just over the bar as Town started to claw themselves back into the game.
61 mins: Hay tried to find Wijnhard with a cross but it was cleared.
59 mins: Zamora's cross drew gasps as it flew in front of Margetson's goal without anyone to convert it. Town were defending deep and not attacking the game.
58 mins: Knight tried to turn in the penalty area but his effort came off Morgan.
56 mins: Jenkins blocked Carpenter and Town began another attack which ended with Kuipers beating Knight to the ball.
55 mins: Holland played a 1-2 with Wijnhard but Cullip cleared.
54 mins: Holland continued to work in midfield, winning the ball, but Brighton continued to attack.
53 mins: Junior Lewis nodded the ball past Margetson after great work by Brooker. Margetson came for the cross but failed to reach the ball as Town allowed the Seagulls in.
52 mins: Kuipers collected the long ball from Chris Hay as Knight raced to try and latch onto it.
51 mins: Hay went round two defenders before losing the ball to a third.
50 mins: Zamora battled away against Gray and wom a throw-in.
49 mins: Clarke gave the ball away and Zamora raced towards the area before falling over. The referee told the Seagulls striker to get up.
47 mins: Knight was felled by a blast in the face from the ball.
46 mins: Hay's shot was inadvertantly blocked by Knight.
A quiet first half was punctuated by Martyn Margetson's late point blank save from Bobby Zamora. Brighton had been keen to play a direct game on their tiny Withdean pitch but Town were generally comfortable as they tried to find their range on the bobbly ground.
Chris Hay came close for Town but couldn't find the target with his close range effort.
47 mins: Zamora was caught offside.
46 mins: Zamora had 2 chances to score after Junior Lewis got away from Thomas Heary and put the lethal hitman through. Martyn Margetson pulled off a superb save and watched Zamora skew his second chance wide.
45 mins: Holland and Hay closed in to defend against Brighton attempts to attack. Town had to defend stoutly.
43 mins: Hay gave the ball away and Zamora went on a rousing run which was stopped by a superb tackle by Nathan Clarke.
41 mins: Knight's challenge on a defender was penalised.
39 mins: Another flowing Town attack was headed clear by Carpenter.
37 mins: Chris Hay's shot whistled over the bar after Wijnhard took control of the ball and picked out Chris Hay.
35 mins: Knight was held off by defenders at the back post as the corner came in. He sat on the ground looking at the referee as play went on.
34 mins: Wijnhard's turn and shot was palmed behind for a corner after a flowing Town attack.
33 mins: Margetson gathered an overhead kick from Morgan after Brighton sent a cleared throw-in right back into the danger area.
32 mins: Watson's free kick hit the wall and Schofield scrambled the ball away.
31 mins: Jenkins looked like he was holding Gary Hart as the ball was played through on the edge of the area. There was clearly a free kick but the home crowd bayed for the red card. The Welshman was booked.
29 mins: Wijnhard almost got on the end of a superb Evans run. The left back crossed but the Dutchman couldn't make use of it.
28 mins: Wijnhard gave the ball away.
27 mins: Margetson dived on the ball after a Brighton attack.
26 mins: Knight tried to play his way through the Brighton defenders but Schofield wasn't there to pick up. Wijnhard squared up to Danny Cullip.
24 mins: Knight's effort from Hay's run and cross was wayward.
24 mins: Gray superbly tackled Zamora on the edge of the Town area.
23 mins: Evans cleared after a period of Brighton pressure - Brooker struck an easy goalbound shot at Margetson which the Welshman saved.
22 mins: Gray was quick to hook the ball away as Hart tried a cross.
21 mins: Holland broke up a Brighton attack in midfield - both sides were closely marking each other.
19 mins: Knight tried to find Wijnhard with an ambitious pass but the ball was too long on the small, bobbly Withdean surface.
16 mins: Margetson dived on Zamora's cross.
15 mins: Morgan and Lewis found themselves onside after Town's offside trap was poor but the two Brighton defenders failed to take advantage.
15 mins: Holland was penalised for an illegal challenge on Bobby Zamora.
14 mins: Town were forced back by determined closing down by the Brighton midfield.
13 mins: Wijnhard lost the ball after chesting it down.
12 mins: Margetson was almost beaten by Gary Hart's first time effort which was laid on by Bobby Zamora.
11 mins: Clarke stole the ball off Zamora and cleared comfortably.
10 mins: Brooker hit the ball long for Zamora but Margetson got there first and cleared.
8 mins: Richard Carpenter needed lengthy treatment after going down injured.
7 mins: Evans' free kick was poor and was knocked away easily.
6 mins: Heary's shot was high.
5 mins: Wijnhard's cross/shot was palmed away by Kuipers after Knight's flicked header fell to the Dutchman.
4 mins: Kuipers was closed down by Knight but the Town striker conceded the goal kick.
2 mins: Evans headed away Watson's set piece.
Danny Schofield returned to his previous position on the left of midfield as Leon Knight replaced the departed Craig Armstrong in his usual attacking position alongside Clyde Wijnhard. Thomas Heary stayed in midfield despite competition from Dwayne Mattis and Kenny Irons.