Firefox will play the file if you have a player installed that supports the mime type that the server sends for that file.

See "File handling in Firefox 3 and SeaMonkey 2": http://kb.mozillazine.org/File_types_and_download_actions

The reply posted Jun 18 regarding mime types is irrelevant to the actual problem. The difficulty is files play instead of downloading regardless of how preferences are set. This means it is virtually impossible to download mp3 arghhhhhh! Any other suggestions would be greatly appreciated!

Although right-clicking on the MP3 link would allow it to be downloaded, I agree that Firefox should respect the preferences specified in the Applications tab of Preferences, and it is very misleading to allow the user to select "Always Ask" for MP3, then completely ignore this due to the presence of a plugin.

Go to about:config (click "I'll be careful, I promise")

Find plugin.disable_full_page_plugin_for_types

Right click on the line of text and click Modify

If there is no value in there then enter audio/mpeg If there are already values add ,audio/mpeg at the end (comma is important)

Click OK Restart Firefox

Now clicking on an mp3 will ask where to download

Thank you for this tip, I was going mad, I had set all the mime types to always ask but firefox always playing mp3s using the vlc plugin instead of asking. I manually created the value and after restarting firefox it started asking what to do! :-)