http://demo.bigbluebutton.org/
There is a open source webconferencing suite available to install at your own server.
https://reports.adblockplus.org/2b0bef8 ... ab=filters
Every instance of BBB can have it's own domain name, so it may be a problem with rules.
Maybe developers of BBB should rename path to css, that will help to avoid this problem in future? (I found this now and will tell them link to this topic).
BigBlueButton installations and their CSS.
Caused by Russian subscription; Submit issue here http://forum.mozilla-russia.org/viewtopic.php?id=3679