Comment # 4 on bug 961143 from Wolfgang Rosenauer

I'm not exactly sure I understand the bug report completely.
So currently it is about Firefox and Seamonkey not being able to play MP3?

If so the first question is which GStreamer component provides the MP3 support
on your system?
For some reason the Fluendo plugin stopped working for current versions of
Firefox. I have no real idea why. It seems to work again if all of GStreamer is
replaced by the newer version 1.6 from packman though.

Please provide a list of installed packages to compare since the example site
above works for me in Firefox.