Perth Glory rose to third on the A-League ladder with a clinical 2-0 away win over a sagging Adelaide United on Thursday night.Striker Billy Mehmet and captain Jacob Burns scored in a victory at Hindmarsh Stadium which hoisted Perth above Wellington Phoenix.Before Adelaide's lowest-ever home crowd of 5898 spectators - more than 4000 shy of their stadium average - the Glory took a sixth minute lead through a controversial goal to Mehmet.Perth's scoring sortie started when defender Dean Heffernan clashed with Bruce Djite on a wing, leaving the Adelaide attacker sprawled on the turf after apparent high contact.As Djite writhed, the Glory thrived with ex-Adelaide skipper Travis Dodd pivotal.Dodd, in vast space, advanced along the right flank and when five metres from goal pulled the trigger with a powerful right-footer from a tight angle.The ball crossed the face to Mehmet, almost on the goal line, and he capitalised although replays showed he was off-side.Adelaide, cemented in ninth spot with just five wins, slumped further behind when an audacious shot from Burns found the net in the 24th minute.Burns, some 20 metres from goal, pounced on a hurried headed clearance from an Adelaide outfit with the worst defensive record in the competition.The Glory skipper launched a brilliant strike with the outside of his right foot which flummoxed his Adelaide counterpart, 'keeper Eugene Galekovic.Perth expertly protected their lead for the remainder of the half with stingy defence allowing the Reds just one shot on target - a speculative strike from Cassio in the fifth minute.It took the Reds until the 77th minute to seriously threaten, when Glory goalkeeper Danny Vukovic fumbled a corner.The spillage fell to Adelaide's Nigel Boogard who slotted into the net - only for the goal to be disallowed by referee Matt Gillett who mistakenly believed Vukovic was interfered with.Adelaide United coach John Kosmina was livid at the crucial refereeing errors, saying Mehmet's goal was off-side and the non-decision "killed us"."It was a clear off-side," Kosmina said."Decisions like that are game changers."And it wasn't like it was line-ball, it was really obvious."Perth Glory coach Ian Ferguson conceded his club was fortunate with the decisions."It's swings and roundabouts, tonight we probably did get a little bit of luck," he said."He (Kosmina) has every right to be a little bit annoyed."But at the end of the day we came here to get three points, we got three points. I'm not going to slag a referee because he's made some bad decisions, we all cop it."