Upgrade your browser to Firefox 9 and check

• getfirefox.com

Swarnava, I do believe he has already been downloading and installing Firefox 9.0.1 three times already.

avowedrep, your user agent appears as if it is Firefox 3.5.19 in more system details link on right of your post.

Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.19) Gecko/20110420 Firefox/3.5.19

See this on how to reset to default. https://support.mozilla.com/en-US/kb/websites+or+add-ons+incorrectly+report+incompatible+browser#w_reset-your-user-agent

As for the "Warning: this version of firefox is no longer supported?" is sounds as if you still have the old http://www.google.com/firefox Firefox start page hosted by Google as your homepage. This old default homepage is no longer used (Firefox 3.6.* and earlier) as about:home has been in use since Firefox 4.0

Either ignore the "You're not on the latest version of Firefox" message, change homepage to about:home, change it to another page or leave blank.

http://support.mozilla.org/en-US/kb/How+to+set+the+home+page

If there are problems with updating or with the permissions then easiest is to download the full version and trash the currently installed version to do a clean install of the new version.

Download a new copy of the Firefox program and save the disk image (dmg) file to the desktop

• Firefox 9.0.x: http://www.mozilla.org/en-US/firefox/all.html

• Trash the current Firefox application to do a clean (re-)install
• 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 if you uninstall and (re)install Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox

• https://support.mozilla.org/kb/Installing+Firefox+on+Mac
• http://kb.mozillazine.org/Installing_Firefox#Mac_OS_X