Nowadays a lot of people are on the web 24/7 (or at least their PCs are) but in the early days, many visits were prompted by special occasions, such as Valentine's Day. Indeed, at one time the web sometimes seemed to be a succession of special events, from Christmas and the Chinese New Year through Easter to Halloween, with a few sporting highlights thrown in (Super Bowl, Tour de France, various Olympics, the Iditarod). This was reflected in my old Web Watch column and a few special features, several of them about Valentine's Day.
February 14 provided a good excuse to go online, send an e-card, find somewhere romantic to go, look up a special recipe, or browse a bit of Valentine's Day history. Check Cupid's Checklist for examples. Apart from specialised sites, it also offered millions of webmasters the chance to add something that might attract new readers, and maybe even sell something. Bring out those Valentine's Day specials on violin cases....
Today, Wikipedia has it pretty much covered, assuming you hit the page when it isn't vandalised. However, since I'm a Big Sex-Biscuit for the day, I'll also point you to the old and undeniably pink Valentine's Day Name Creator. "Warning: This might make you feel ill."