What is the speciality and significance of the valentine day?

Valentine's Day is a traditional day on which lovers express their love for each other.The day is most closely associated with the mutual exchange of love notes in the form of "Valentines". Before 3 or 4 years Valentines Day was just like any other day when no one used to notice it and it used to just come and go away, but nowadays people start preparation for it as if it is a big festival and there are lot many inventing ways of opposing it.