"...how do I go back to 28?" To be clear, using old versions of browsers poses a significant security risk— possibly to your personal info and/or system. That having been said, you can find Firefox 28 on mozilla's site: http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/28.0/win32/en-US/ All other versions are here: http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/

There may be other causes for the increased memory usage. Create a new profile as a test to check if your current profile is causing the problem. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox ---- See also: *https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox *https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox *https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox *http://forums.mozillazine.org/viewtopic.php?f=38&t=2824649