Sometime back, after upgrading FF versions, some websites didn't properly display. Best way I can describe it is parts of the screen overlayed other parts. Only a few sites. But it made those sites unusable.
IE & Chrome didn't have the problem. Waterfox acts exactly the same as FF.
But Portable Firefox works fine. v18.0.1 I suspect knowing that fact is the key to solving my problem.
No, this has been a problem for a long time, and although I thank you for the suggestions (and tried them), the solution will only come from somebody who understands why Portable works and regular FF doesn't.
I note again that all browsers except FF have no problems with any sites. And I didn't do the 'Transferring data to a new profile - Firefox' thing. Would using the profile of Portable be a good idea? My FF profile is about 20 years old.