Thanks Toufig,
The precise technial problem with it working in one browser and not another is still unclear. I understand the likely cause, but not the precise resolution.
I caused the issue I believe. I was having some difficulties in early design of the home page (attempting to fix something displaying incorrectly on the page layout) so decided to create a new home page. I could not delete the original so had to create a home2 first, delete the original home page and then rename the new page to HOME. The issue then arose that when One creates a new page, it will have a new page ID. I think that was the likely cause of the issue.
I probably could have fixed the issue in the PHPMyAdmin at the database level but since I was not very far along in design, it was more prudent to serially retore from backups until I restored to the earliest point prior to my big mistake.
Once I restored, I reloaded the Scuba Diving layout for the home page and it worked fine in ANY BROWSER TESTED.
So my solution was not brilliant rocket science but more of a failute-to-fix and resorting to restoring from a good backup.
There is still a glitch in the lower part of the content area where the text area gets covered up by a background image. (This is what I was attempting to fix when my initial problem arose). . So before trying to fix things again I will do another precisely-timed manual backup before making any attempts to fix the issue.
Thanks for your help.