Gecko is the underlying engine of Firefox (like V8 for Chrome), I meant R3dfox.
They are basically just new versions of Chrome (Supermium) and Firefox (R3dfox) respectively, designed to run on legacy systems, like how Supermium can go back to Windows 98 I believe (
). If you can’t or don’t want to update to a newer version (because windows 7 is sick), then I would recommend downloading one of those rather than trying to hang onto old Firefox.