Shawn Crawford stormed to victory in the 200m, but the race will be remembered for the remarkable behaviour of the crowd in the Olympic Stadium.
The start was delayed by over five minutes as the home fans voiced their support for absent defending champion Kostas Kenteris of Greece.
Pre-race favourite Crawford eventually took gold, ahead of fellow Americans Justin Gatlin and Bernard Williams.
But at the finish, the boos rang out again in protest at Kenteris' absence.
The Greek sprinter, along with compatriot Katerina Thanou, pulled out of the Games after missing a drugs test.
Elsewhere, Steve Backley scraped into the javelin final in his last major championship.
Backley looked to have ended his career on a low note when his best throw of 80.68m fell short of the automatic qualification mark.
He had a nervous wait as he watched the second group of athletes throw but he eventually placed 12th - the last berth for Saturday's final.
Kelly Holmes' dreams of double gold remain alive after she qualified comfortably for Saturday's 1500m final, putting in a trademark fast finish to take second in her semi-final.
Felix Sanchez, unbeaten since 2001, finally picked up an Olympic gold medal in the 400m hurdles, ahead of Jamaica's Danny McFarlane and France's Naman Keita.
Chris Tomlinson just missed out on a medal in the long jump after finishing in fifth place thanks to an opening round effort of 8.25m.
The gold went to favourite Dwight Phillips who leapt an astonishing 8.59m with his first jump.
Ricky Soos failed to reach the 800m final after coming sixth in his semi-final behind world record holder Wilson Kepketer of Denmark.
Gold medal favourite Ladji Doucoure made it to the 110m hurdles final without any trouble, beating American rival Terrence Trammell in his semi-final.
And the United States looked hugely impressive as they clocked 41.67 seconds in qualification for the women's 4x100m final.
Britain's hopes of more medals have been buoyed by the news that Paula Radcliffe has entered the 10,000m.
Radcliffe registered for Friday's final and is set to confirm whether she will participate on the morning of the race.
Earlier in the day, sailors Chris Draper and Simon Hiscocks won Team GB's 25th medal of the Games, taking bronze in the 49er class.
In canoeing, Britain's Ian Wynne qualified for Saturday's K1 500m final with a dominant display, winning his semi and clocking the fourth fastest time.
Lucy Hardy made the final of the women's event after being promoted from fourth to third following the disqualification of Poland's Aneta Pastuszka.
Elsewhere, Hamish Carter of New Zealand won triathlon gold, finishing seven seconds ahead of compatriot Bevan Docherty, the world champion.
The USA progressed to the last four of the basketball tournament following a 102-94 victory over Spain.
Lithuania also reached the semi-finals on Thursday with a comfortable 95-75 win over China and they will face Italy, who beat Puerto Rico.
USA won a tense women's football final, beating Brazil 2-1 in extra time with a headed goal from Abby Wambach.
The taekwondo event got under way on Thursday, but there was disappointment for Britain's Paul Green, who was hampered by injury as he went out at the quarter-final stage of the under-58kg category.
At the Aquatic Centre, Greece narrowly failed to win their seventh gold medal of the Games when their water polo team were narrowly beaten 10-9 by Italy after extra time.
The USA took bronze after a 6-5 win over Australia.
Germany beat bitter rivals Holland 2-1 to take gold in the women's hockey.
World champions Argentina needed a 70th minute strike from Luciana Aymer to beat China 1-0 and take the bronze.
Despite starting the 3km run with a slim 11-second advantage, Andrey Moiseev of Russia comfortably took gold in the men's modern pentathlon.
The women's event, in which Kate Allenby and Georgina Harland are both hopeful of winning medals for Britain, takes place on Friday.
Away from the action, the IAAF has announced it will launch an inquiry into the missed drugs tests of Greek sprinters Kostas Kenteris and Katerina Thanou.
Matthew Pinsent has been voted off the International Olympic Committee despite winning a fourth gold medal at these Games.
It was also announced that rower Olena Olefirenko failed a drugs test. As a result Ukraine's women's four have lost their bronze medals.