For Firefox to automagically play RealPlayer files, you need to have
- nphelix.so in firefox/plugins
- nphelix.xpt in firefox/components
These are copied from the RealPlayer/mozilla directory.
You must do this as the user that installed Firefox (probably root) and Firefox must be started once by that user after copying these files (see
http://getfirefox.com/releases for the details).
It would be far, far better if RealPlayer were installed in /usr/local rather than your home directory. In that case, you would add /usr/local/RealPlayer to the PATH environment variable in /etc/profile; if not that, make sure that /home/mques/RealPlayer is on your local PATH environment (see the README in the RealPlayer directory).