The Web site of greeting card giant Hallmark has been overwhelmed by requests to make and view Valentine's Day e-cards, and is currently down.

AlertSite, a Coconut Creek, Fla.-based Web site metrics provider, noted that starting as early as 7 a.m. EDT Hallmark.com began experiencing problems. When it polled the site at 7 a.m., only 28 percent of the requests got through, and response times surged to nearly three seconds for those who did manage to connect. Although the site's performance improved by 8 a.m., it fell again the hour after that. By 10 a.m., the site had gone offline.

As of 1 p.m. EDT, the site still displayed the message, "Hallmark.com is temporarily offline for maintenance. We want to make sure our site is the best it can be, so we're doing a bit of house cleaning. We expect to be back online shortly."

About 1 billion traditional cards are exchanged on Valentine's Day, making it the second-biggest card-sending occasion of the year after Christmas.