#A link to Firefox 4 versions will not be offered by any '''''responsible''''' contributor here, because Firefox 4 versions contain stability and security issues <u>that will not be corrected</u>. Firefox 4 is a thing of the past. #The only currently supported versions that a '''''responsible''''' contributor here will offer are Firefox 5 and Firefox 3.6.18. Firefox 3.6.18 is currently scheduled for support for only 2-3 more months, then it, too, will be a thing of the past. Firefox 6 will probably be introduced about the time the Firefox 3.6.18 support is discontinued. #To downgrade to Firefox 3.6.18, follow these instructions '''''very carefully''''': #*Back up your personal information (bookmarks, passwords, etc.) before proceeding just in case something goes wrong: https://support.mozilla.com/en-US/kb/Backing%20up%20your%20information #**'''''If you need to''''', see the following article. See the last 2 sections "Copying files between profile folders" and "Your important data and their files" to restore important information '''''if something goes wrong in the downgrade''''': https://support.mozilla.com/en-US/kb/Recovering%20important%20data%20from%20an%20old%20profile #*Download and SAVE Firefox 3.6.18 to your Desktop, then proceed as in the "Clean re-install" article below: https://www.mozilla.com/en-US/firefox/all-older.html #*Clean re-install: http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall #*You may also need to reset your extension databases in your profile folder. Do the procedure after locating your profile folder (see "Back up your personal information" above) and closing Firefox. The files will be automatically re-built when you re-start Firefox: http://kb.mozillazine.org/Unable_to_install_themes_or_extensions_-_Firefox#Corrupt_extension_files