Debian comes with totem as the default media player, and totem-mozilla provides plugins for iceweasel and its ilk, to view video clips embedded in web pages.
I prefer mplayer (from the Debian multimedia package repository) and mozilla-mplayer - while, in my opinion, mplayer itself is just marginally better than totem (my old laptop is challenged by both), the mplayer browser plugin is much better: embedded video clips look very similar to what you see on Window$ (with an added bonus of full-screen display), you can control the percentage of the clip that has to be downloaded before playback starts (I set it to 100% - I hate the stalls), and you can save the clip, copy its URL and more.
The totem plugin supports some mime-types that the mplayer plugin doesn't, so I keep it installed, just in case. The problem here is that when totem-mozilla is upgraded, it overrides the mplayer plugin. This can be verified in the browser via the about:plugins page - the totem plugin shows up on the top of the list - and I want mplayer to be first. But, unlike extensions and themes, there doesn't seem to be a way to manage plugins in iceweasel.
The seemingly obvious solution is to reinstall the package:
aptitude reinstall mozilla-mplayer
but this doesn't help.
dpkg -L mozilla-mplayer
to list the files that are installed by this package, and found that the plugin files (.so and .xpt files) are installed at /usr/lib/mozilla/plugins.
My guess was that iceweasel sorts the plugins by the modification date of these files, so I updated their modification date (as root) like this:
I was probably right - it fixed the ordering of the plugins, and mplayer is again the default multimedia plugin.
Back to my favorite pastime activity: watching movie trailers.