Traditionally, a bride stands to the left of her husband on their wedding day and at social events. However, these days it is rare for a wife to purposefully stand to the left of her husband.
The reason a wife would traditionally stand to the left of her husband is because a man's right arm was considered his sword arm. Should a husband have to protect his wife, he would hold her in his left arm and fight off any danger with his right arm. It was therefore in the wife's best interests to always stand on the left of her husband.