here's what I found on google
[url=http://en.wikipedia.org/wiki/Drop_kick#American_and_Canadian_football]http://en.wikipedia.org/wiki/Drop_kick# ... n_football[/url]
In both American football and Canadian football, one method of scoring a field goal or extra point is by drop-kicking the football through the goal.
The drop kick was often used as a surprise tactic. The ball would be snapped or lateraled to a back, who would perhaps fake a run or pass, but then would kick the field goal instead.
This method of scoring worked well in the 1920s and 1930s, when the football was rounder at the ends (similar to a modern rugby ball). Early football stars such as Jim Thorpe and Paddy Driscoll were skilled drop-kickers.
In 1934, the ball was made more pointed at the ends. This made passing the ball easier, as was its intent, but made the drop kick obsolete, as the more pointed ball did not bounce up from the ground reliably. The drop kick was supplanted by the place kick, which cannot be attempted out of a formation generally used as a running or passing set. The drop kick remains in the rules, but is seldom seen, and rarely effective when attempted.
The only execution of the drop kick in recent years in the NFL was by Doug Flutie, reserve quarterback of the New England Patriots, against the Miami Dolphins on January 1, 2006 for an extra point after a touchdown. Since Doug Flutie estimated that he had "probably an 80 percent chance" of making a drop kick and regular place-kicked point after attempts have a much higher probability of being good, the kick was not a strategic move. After the game New England coach Bill Belichick said "I think Doug deserves it" and Flutie said "I just thanked him for the opportunity". This was the first successful drop kick in the NFL in over 64 years since it was executed by Ray "Scooter" McLean of the Chicago Bears in their 37-9 victory over the New York Giants on December 21, 1941 in the NFL championship game at Chicago's Wrigley Field. Though it wasn't part of the NFL at the time, the All-America Football Conference saw its last drop kick November 28, 1948 when Joe Vetrano of the San Francisco 49ers dropkicked an extra point after a muffed snap against the Cleveland Browns.
Prior to Flutie's historic drop-kick, the only recent vocal proponent of the drop-kick in the NFL had been Jim McMahon, quarterback for several NFL teams. During the 1980s, while playing in Chicago, McMahon regularly practiced the drop kick, and was known to frequently petition Bears head coach Mike Ditka for an opportunity to use the maneuver. Ditka, who regarded the play as an anachronism, never allowed it.
In August 1974, Tom Wilkinson, quarterback for the Edmonton Eskimos, attempted a drop-kick field goal in the final seconds of a 20-2 romp over the Winnipeg Blue Bombers. He missed. This may have been the last time the play was deliberately attempted in the CFL.
Exclusively in Canadian football, the drop kick can be attempted beyond or behind the line of scrimmage. Any player on the kicking team behind the kicker, and including the kicker, can recover the kick. A drop kick that goes out of bounds is considered a change of possession.
During one game in the 1980's Hamilton Tiger-Cats wide receiver Earl Winfield was unable to field properly a punt and in frustration he kicked the ball out of bounds. The kick was considered a drop kick and it led to a change of possession and the team that punted regained possession of the ball.
The drop kick is most often used as a desperation play at the end of a game.