To downgrade to Firefox 3.6 first uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data.

You can then install the latest version of Firefox 3.6 available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc.

To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations.

For details of how to find your profile folder see https://support.mozilla.com/kb/Profiles

What problems are you having with Firefox 4?

I will be deleting Firefox 4.0 and installing a clean copy of the older version, too - I used to be able to listen to CNN on my computer, all day long. Then when I "upgraded" to Firefox 4.0, suddenly I am not able to listen to CNN on my computer any more. I have already spent way too much time trying to find a solution. It seems like going back to the previous Firefox version will be the best answer. Thank you, TonyE, for your help.