Previewing a persona only works on sites that are whitelisted via an allow exception.

Tools > Options > Security : "Warn me when sites try to install add-ons": Exceptions

Make sure that you do not use Delete browsing, search and download history on Firefox to clear the 'Site Preferences'.

See http://kb.mozillazine.org/Themes#Lightweight_theme

I tried adding the site to the exeptions list, but it did not work. I later found that Mozilla had actually flagged and blocked that add-on as a threat to my system. I unistalled the app and then re-installed it and it sort of works now. However, I can still only preview personas by clicking on the fox in the lower left corner. When I rollover personas on the webpage it does not work.

OK so I added the WRONG website to the list. I added mozilla.com as an exception, but you need to add getpersonas.com to the list. Everything is working perfectly now! Thanks corel