Question Author
rojash, The reason I assumed that they were unacceptable was because the website came back with an error message to the effect that the file name was not recognised.
squarebear, I was using jpeg, which was the specified format.
Thank you all for your help and suggestions. After a couple of hours of trial and error I have finally completed that task. I have a lot less hair than I started with, and that wasn't much.
Thanks to you all again.