Yesterday a friend told me about the Wayback Machine, which has been archiving the web since 1996 or so to preserve sites that disappear. If you google Wayback Machine, you will find a link to a place where you can enter the URL of the site you're looking for. And voila! There were numerous versions of "Jens Bjørneboe in English", archived at different stages along the way. The latest link is:
My other disappeared websites, including my poetry site, seem not to have been archived, but that's OK. This was the crucial one, an internationally known resource on an important Norwegian writer.
Thank you, Tony, for pointing me to this invaluable resource!