Hi, I am doing a website for this guy and I'll be editing it. He wants to sometimes edit it too. Is there a way that we can both edit it?

Right now we both have yahoo site builder installed onto our computers. He can still edit it right now. When I go to file, import a yahoo site, the upload process almost completes and then it fails. It says that it cant upload image files. So right now I have the site on my computer, but none of the images are there.
Is there a reason that the images wouldn't import from the site.

Please Help

Thanks In Advance