Captain Gary Doherty was sent off for Norwich as manager Bryan Gunn lost his unbeaten record in their defeat by Bristol City at Carrow Road.
Robins defender Bradley Orr converted from the spot in first-half stoppage time after Doherty had been dismissed for a crude challenge on Dele Adebola.
The dismissal proved decisive as the Canaries were unable to regain a foothold in the game.
The Robins held on for their fourth consecutive league victory.
Norwich boss Bryan Gunn: "The lads did everything they could to get something out of the game but did not get the support they needed from the people in charge of the game.
"I went to speak to (referee) Mr D'Urso immediately after the game but I am a bit new to this management lark and he told me I had to wait for 30 minutes.
"So 30 minutes and one second later I went to see him and I didn't get much back to be honest."
Bristol City manager Gary Johnson: "We are on a very good run at the moment and it is obviously very pleasing.
"Not so long ago we were in the bottom half of the table and we are trying to make sure we did not get dragged into the relegation area.
"Now we can go into the final third of the season with a chance of pushing for a top-six finish and we are all really looking forward to the challenge."
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