User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0 Installed Better Gmail Extension and then later uninstalled the same. But the prferences created by the extension were still there. The same happens with other extension also. There should be a way of associating the extension with the preferences created and later delete the preferences at the time of the extension uninstallation. Reproducible: Always Steps to Reproduce: 1. Install an extension with creates preferences. 2. Uninstall the extension. 3. Check at about:config, the created preferences will not be deleted. Actual Results: The associated preferences are there. Expected Results: The associated preferences should be deleted. The # of preferences will become too huge with the number of extension installation/uninstallation. Might slow the performance at some point of time.