There's no problem with losing the contents of the Index file (or any other file) so long as I don't change from one project to another and then change back to the original project. If I do change projects, and then change back to the first project, when I open the Index page for editing in the HTML editor (paid version), the entire contents of the Index page is missing -- except for a few lines of code at the top of the page. The only way I can recover the Index page is from a backup, or by downloading the current Index page from the website.
I am trying to work alternately on two separate Projects: These are:
(Project 1) For editing and adding content to my existing website and;
(Project 2) For creating a completely new website that will eventually replace the old one.
All pages are saved before exiting the HTML Editor, or before changing from Project 1 to Project 2.
In case I'm missing something very obvious -- which is quite likely -- could you let me know why I'm losing my Index page contents (not the contents of any other pages) whenever I change Projects.
Many thanks
Gordon Lyons.

If you can replicate this I would open a support topic so the CC gurus can take a look at your setup.

Hi Eric,
Many thanks for your quick response. I wasn't expecting a reply until after the holiday period, so there's no need to follow this up until then. Enjoy your break!
I tried to replicate the problem to send you attachments or screenshots of the Index page.
Usually, I just close all the open files before opening the other Project - although by doing it this way, the list of web / computer files still remains open in the left hand panel. It was on those occasions that the Index page lost its content.
This time, however, I tried a different method: I closed the files I was editing, then I exited Coffee Cup HTML Editor completely. I then restarted the Editor before selecting my other Project. I used the same procedure when switching back to my first Project. This time, the Index file remained intact and I had no need to use the backup. If that's all I need to do to preserve the Index page intact, I'll just follow this procedure in future.
I wonder if you could clarify something for me (after the holidays)? You emphasize the necessity of using Projects, and this is what I've been trying to do with each of the two websites. However, in the CoffeeCup Software folder, there's both a 'project' folder and a 'mywebsite' folder. In which of these folders should I place my two website Projects?
Many thanks for all your help, and wishing you all the best for Christmas and the new year.
Gordon Lyons
Air Crash Sites-Scotland