Thank you, Harald, for your thoughtful reply. I don't understand some of your comments, however.
The portfolios themselves are created by Lightroom. I have neither the knowledge or interest to create these myself. So, I have no control over things like going back to the home page or "tabbing" from one photo to the next. What LR produces is what it is (and pretty good, I think).
I don't know what you mean by "tabbing." Do you mean "clicking" (with the mouse)?
As for opening the home page photos in a new window, I think this is important and it was intentional. The home page and the photo remain on-screen.
Anyway, thanks for replying.
OK, I didn't know that your web-site is straight from Lightroom. Indeed, this will limit your options compared to web-sites made by wordpress et al.
Tabbing is the acronym for a mouse-click on a tablet-computer. It is "learned" that tabbing on the left side of a picture leads one picture back while tabbing on the right side will proceed.
I know that it's your web-site and it's your decision, but I will try another approach to persuade you out of opening a new window within a web-site. Some users don't use tabbed browsers and it's quite inconvenient for them to return to the home-page.