[Last updated 10 August 2018]
The Bookmark function has been running for 6 months. I was never happy with its implementation, but I couldn’t find anything better.
However, I now find that is interfering with other parts of the site, slowing things down, and leaving remnants of itself in the oddest of places.
So I have now removed this functionality from the site.
All is not lost: every web browser has a similar function, called either Bookmarks or Favourites. Simply create Bookmark/Favourite folders in your browser, then when you have found a page on my site that you know you will want to keep returning to, just add that page to your Bookmarks/Favourites.