The charge related to an incident during Forest's trip to Bournemouth on April 26 and it was not contested by Halford.
The incident was not spotted by match officials during the game but was subsequently highlighted on video.
Halford's ban starts with the final game of the 2013-14 season, the visit of Brighton on Saturday, and will run into the first two games of next season when Stuart Pearce will be in permanent charge.
His absence leaves Forest with a defensive headache, as Jamaal Lascelles, Kelvin Wilson and Jack Hobbs are all unlikely to be fit to face the Seagulls.
Kevin Gomis, who has made only one appearance since arriving at the club on loan from Nice, could get a start alongside Danny Collins.