Who hasn't heard of a PNG? There is more than 1 program to design websites you know. They are basically the exact same thing as a PSD, except ones file version is for Photoshop and the other is for Fireworks. You can export it out as a PSD from Fireworks anyway.

Although I've not worked with Fireworks much, every PNG I've ever recieved is an absolute ton smaller than PSDs, which often range up into high XX for a fairly heavy design.