I made some changes to my computer the other day and now have no idea how to fix what may have potentially caused the thumbnails on youtube and facebook to no longer display. I checked to see if the thumbnails worked in Internet Explorer and Chrome and they did, so I know the problem is linked to Firefox. Did a websearch to see how to fix this issue and tried each method to no avail. This included: disabling add-ons, changing the cookie settings, deleting history, checking settings under about:config. None of this worked. I don't know what to do! It might be an actual computer setting, as opposed to a firefox setting, but I can't remember what I did or where.