Using parent.location = anyUrl solves the problem (and works with both target=_top and target=_parent)
For several reasons, it isn't practical to change the file extensions for this site. So I followed the thread Torka suggested, to the info on using PHP on a page with an HTML extension. I've emailed the server owner for this site to see if the technique will work on his server.
If so, I will go with SSI. If not, I will fall back on the Iframe. In future, I will be focussed on the SSI solution as it seems much better.
Many thanks to everyone for your ideas. Have a happy & healthy year-end!
Skater 50









