Hello mariemconlin, probably you mean that you can not update firefox. Please download a new copy of firefox and then install that new copy of firefox, try next steps: 1. Download a copy of the latest firefox from http://www.mozilla.org/en-US/firefox/all.html (full dmg package) 2. '''Trash''' the current Firefox application to do a clean install. 3. Install the version that you have downloaded. '''Do not select to remove your personal data''', your profile data is stored elsewhere in the [http://kb.mozillazine.org/Profile_folder_-_Firefox#Mac Firefox Profile Folder], so you won't lose your bookmarks or other personal data. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac thank you