PlantFiles is getting a new look! Just in time for spring, we're rolling out a new look for the best online plants database. It will also work with your smart phones and mobile devices, so now you can take it with you on garden center visits or botanical garden tours. Questions or comments? Please post them here.
Can you say more about what happened to them? Or how you started them/conditions/watering/etc? Damping off is a very common fungal disease that kills seedlings and it's caused by keeping things a bit too wet. In the absence of any other information that would be my guess and I'd tell you not to water as much next time, but with a bit more info someone might be more helpful.