Try to create a plugins folder in the Firefox Profile Folder and place a symlink to the JP2 Java plugin file (libnpjp2.so) in that folder. *http://kb.mozillazine.org/Profile_folder_-_Firefox *http://kb.mozillazine.org/Java You can use this button to go to the Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Open Containing Folder

Also, Exit Firefox and rename the '''pluginreg.dat''' in your profile folder and start Firefox again. This may help to reinitialize the plugins that Firefox recognizes. ............................................................................................................................... Useful links: [https://support.mozilla.com/en-US/kb/Options%20window All about Tools > Options] [http://kb.mozillazine.org/About:config Going beyond Tools > Options - about:config] [http://kb.mozillazine.org/About:config_entries about:config Entries] [https://support.mozilla.com/en-US/kb/Page%20Info%20window Page Info] Tools (Alt + T) > Page Info, Right-click > View Page Info [https://support.mozilla.com/en-US/kb/Keyboard%20shortcuts Keyboard Shortcuts] [https://support.mozilla.com/en-US/kb/Viewing%20video%20in%20Firefox%20without%20a%20plugin Viewing Video without Plugins] [http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox Profile Folder & Files] [https://developer.mozilla.org/en/Command_Line_Options#Browser Firefox Commands] [https://support.mozilla.com/en-US/kb/Basic%20Troubleshooting Basic Troubleshooting] [https://support.mozilla.com/en-US/kb/common-questions-after-upgrading-firefox-36 After Upgrading] [https://support.mozilla.com/en-US/kb/Safe%20Mode Safe Mode] [http://kb.mozillazine.org/Problematic_extensions Problematic Extensions] [https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes Troubleshooting Extensions and Themes] [https://support.mozilla.com/en-US/kb/Troubleshooting%20plugins Troubleshooting Plugins] [http://kb.mozillazine.org/Testing_plugins Testing Plugins]

cor-el and Vivek.Wilfred, Thank you very much for your swift replies! In the end, I managed to solve my problem for all users of my computer at once by creating a symbolic link in the directory /usr/lib/firefox-addons/plugins to the file /usr/lib/jvm/java-6-sun/jre/lib/i386/libnpjp2.so. the two important points were (1) to use libnpjp2.so instead of the file libjavaplugin_oji.so, as indicated on http://plugindoc.mozdev.org, and (2) to put this into /usr/lib/firefox-addons/plugins.