I have a new version that I think works except I can’t Execute script upon navigating back to a page. Currently I must refresh a page to get a new setting but otherwise I think everything else works. What I am doing now is to use alternate stylesheets.
Well this is interesting. I uploaded the new script and now it does not have the problem of the page not changing. I did not yet update the description in the site very well; I will do that later.
I found Alternative Style Sheets - CSS | MDN and that explains things better than anything I found previously. Using the new script when my site is browsed with Firefox we should be able to use “View” | “Page Style” to switch the style. Oh, I just now realized that if we use Firefox then the change won’t be saved. My script will save the setting whether we use Firefox or any browser that supports local storage.