Christian legend says that Valentine’s Day is the Feast of St. Valentine.
In 270 A.D., the Roman Emperor Claudius II did not want any marriages to take place during wartime. He believed married men made poor soldiers.  But Bishop Valentine went against his wishes and performed wedding ceremonies.
Valentine was jailed and then executed on February 14, by order of the Emperor.
Hence, the name and celebration of love on February 14.

In another story he was a priest that also cared for the sick. In this story he was executed merely for his beliefs. In either case on the day he was to be executed (February 14) he had a visitor and gave her a  note to reassure her that said "from your Valentine" -- this seems to be the origin of the tradition.

Approximately 1 billion Valentine's Day cards are sent each year.

In order of popularity, Valentine's Day cards are given to: teachers, children, mothers, wives, sweethearts, Koko the gorilla.

The expression "wearing your heart on your sleeve" comes from a Valentine's Day party tradition.

Young women would write their names on slips of paper to be drawn by young men. A man would then wear a woman's name on his sleeve to claim her as his valentine.
People also believed that birds began mating on February 14.

The idea of lovebirds soon became associated with Saint Valentine, and the custom of sending cards or small gifts on his feast day is centuries' old. As for the heart-shape cards: Since ancient times, the heart has symbolized love, both human and divine.

15% of U.S. women send themselves flowers on Valentine's Day.

The record for the most couples kissing at once is 1600.

Valentine's Day is the second largest card-sending holiday in the United States.
In Wales wooden love spoons were carved and given as gifts on February 14th.
Hearts, keys and keyholes were favorite decorations on the spoons. The decoration meant, 'You unlock my heart!'

Red roses are the single most popular flower to give on Valentine's Day. Although they may all look the same to the untrained eye, there are actually more than 900 varieties of dark-red and medium-red rose, according to the rose lovers' web site, www.everyrose.com .

Chinese Valentine's Day is not celebrated on February 14, but on the seventh day of the seventh month of the Chinese lunar calendar.

Updated 4th February...