A white wedding is a traditional formal or semi-formal Western wedding. The term refers to the white color of the wedding dress, which became popular in the Victorian era, after Queen Victoria wore a white lace dress at her wedding. Various theories for the meaning of this color choice have been put forward, from an appreciation of color symbolism, to represent purity of heart and the innocence of childhood, to an effort by the monarch to promote lace sales, to conspicuous consumption by status-conscious families, because a white dress could be easily damaged and was therefore common only among wealthy families. Later, it was believed that the color white symbolized virginity and should be worn only by a virgin bride.
Source : http://en.wikipedia.org/wiki/White_wedding