https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac https://support.mozilla.org/en-US/kb/firefox-osx Your settings like Bookmarks, Passwords and such are located in a separate place and not in the Firefox folder. https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

To add a bit more detail: You can download the '''OS X''' installer file for Firefox 45 ESR, using any browser, from this page: https://www.mozilla.org/en-US/firefox/organizations/all/?q=English%20%28US%29 <-- this link is for English (US) Once you save the Firefox 45esr .dmg file to your computer, you can THEN uninstall Firefox 48 before installing Firefox 45 ESR. The article [[Uninstall Firefox from your computer]] explains how to uninstall the Firefox application (simple! just open the Applications folder and drag the firefox.app to the trash). Just do that. DO NOT remove the Firefox profile (user data and settings) since you can keep that for Firefox 45 ESR. I also have an old Mac running 10.6.8 . When the time comes, I plan to remove Firefox 48 from the Applications folder and then replace it with Firefox 45 ESR. _{In case you (or anyone else) is interested, you can have multiple copies or versions of Firefox installed into different locations. I downloaded and installed Firefox 48 in a new "Firefox48" sub-folder of Applications, even though I already have Firefox 48 in Applications. I plan to install Firefox 45esr when Firefox 48 becomes outdated but I wanted to also have Firefox 48 available for other reasons (mainly the new about:profiles feature).} Hope that helps. Alice