Why Do Some Cars Drive on the Right Side of the Road and Others on the Left Side?

If you have ever traveled to a country where people drive on the opposite side of the street, it may confuse you a bit. I often look the opposite way when crossing the street and almost get hit by oncoming cars. Not to mention the driving itself, which is nearly impossible to get used to.
During the 1700's, horse-drawn coaches were very popular in England. The coachman would sit on the right side of the carriage. If they drove down the right side of the street than they would end up whipping pedestrians instead of their horses. By staying to the left, the coachman would have enough room to whip the horses. 

In France, people drive on the right side of the road because of the horse and buggy. The French coachmen rode on the left side and sat on the left side. The horses would often pull to the left and go on the sidewalks. In order to protect the pedestrians they were ordered to stay on the right to protect them. 

Source posted by Julia