Hi Brenda, - have been going over your page (using it as a learning tool) and think it's pretty much there now. Have been testing it here and haven't found any holes, but I now have form-code blindness and may have missed a testing permutation.
Could you give it a thorough testing please and post back if you find any problems?
I have zipped and attached the revised page.
Update: Fixed the 'Show If' server behaviour for multiple checkboxes.