Version for up to Firefox 44 Rated 4 out of 5 stars

I have edited to create a version that works on Firefox 44 Available here:
Please read all the info on that page before installing

not really working in FF12 Rated 5 out of 5 stars

Thanks @raindress for instructions to force compatitbility with FF12, but bookmark previews is quite crippled in versions of FF > 3.5 The previews are tiny and you can't expand the pane that they are in (which is now at the bottom rather than at the top)
I have looked at the code and the bookmarks "page" in FF has changed quite considerably since FF 3.5 which is why bookmarkpreviews doesn't work as before. On my longterm plan to try to get the code working and will definitely post here if I do.

By the way no need to refresh previews. They are saved in:

Documents and Settings\'user'\Application Data\Mozilla\Firefox\Profiles\xxxxxxxx.default\bookmarkpreviews\

where 'user' is your user name and xxxxxx is a random list of characters. If you back these up and restore after installing bookmarkpreviews then it will pick them up.

Will be updated. Why not DONATE Rated 5 out of 5 stars

This addon is indispensible to me. The developer has indicated that he does intend to update the addon for FireFox 4. All of you complaining about the lack of updates - just DONATE. I have. It's the best way to show your appreciation and guarantee that this addon will continue to be developed. I have been in email communication with John and he is keen to do the update. Support him - DONATE NOW - don't wait until the update comes out.
There's a donate button on the support site: