In can't install Firefox 3.6.3 on my iMac 10.5.8. I always get the message saying I don't have the requested authorization to install some elements, despite I'm amdinistrator of the iMac
Problem installing Firefox 3.6.3 (french version) on my iMac running with Mac OS X 10.5.8
See http://kb.mozillazine.org/Installing_Firefox#Mac_OS_X ..... Download a new copy of the Firefox program: http://www.mozilla.com/firefox/all.html Trash the current Firefox application to do a clean reinstall. Install the new version that you have downloaded. Your profile data is stored elsewhere in the Firefox Profile Folder, so you won't lose your bookmarks and other personal data.
See also Upgrading to Firefox 3.6