According to GB there are no popups on GBO, so I'm sure I have no idea what you are talking about.
Of course, I've been using Firefox and AdBlockPlus (along with No Script and DoNotTrack) for a long enough time it could be advertising Armageddon and I'd not notice!
(Sarcasm aside, this approach was mentioned in Forum Support a while back, so AdBlockPlus or becoming a GBO supporter by sending money are the two official ways I know of to rid the forums of the ads.)