Championship strugglers Yeovil Town have earned a vital win at Watford despite being under pressure for large periods of the game.
The Hornets looked the more likely to take the lead early on when Fernando Forestieri's 20-yard shot flashed narrowly wide of Wayne Hennessey's goal.
Watford continued to probe with Marco Cassetti almost finding a breakthrough when he rose to meet Troy Deeney's cross, but had his header was blocked by Liam Davis.
Davis made the hosts pay for their profligacy in front of goal when his ball to the far post found Byron Webster, who nodded home in first-half stoppage time.
Watford's bad luck worsened eight minutes after the interval when Nottingham Forest loanee Ishmael Miller headed home Joe Edwards's cross from close range to increase Yeovil's lead.
Edwards added to the Hornets misery when he netted a third goal in stoppage time to seal the victory.
The Somerset club are now off the bottom of the Championship, but have a five-point deficit to the sides outside the relegation zone.