Bug in (Mac) Firefox? [Plugin-Download Request]

I just heard from a partner using Mac and Firefox that when opening the page he was requested to download an additional Plugin to display additional content of the page. When prompting to download FF returns with the note "no such plugins found".

I just want to clarify if this bug is caused by anything on the Gavick template side or by any additional extension we added, as I have no chance to test it myself on a Mac.

Can anyone report about this issue too?

Thank you very much!