This site has been inundated with links and visitors in the last few hours. While it's lovely to have you stop by, basically too many synchronous requests to the card-sending functionality has caused the server to b0rk.
Imagine that this site is a house I'm renting and hundreds of thousands of people all pile around for a visit. Now, there isn't a problem at all until you all want to use the bathroom at the same time. The door simply isn't wide enough for you to all squeeze through at once, and I can't get you all to form an orderly queue, so unfortunately the owner of the property (my webhosts) have insisted that the bathroom facilities have to be suspended for the moment. It's a ropey metaphor, I know, but I hope it helps to explain the problem. I'm working on a fix, but don't hold your breath. Sorry!
So next year be sure to send your Anti-Valentine E-Cards early!