Firefox settings

settings.txt

# "services.sync.prefs.sync." <- prefix this for FireFox to sync it across all logged in browsers.
browser.link.open_newwindow = 3 # Open everything in new tabs
browser.link.open_newwindow.restriction = 0 # Force new tab for script windows as well
browser.tabs.unloadOnLowMemory = true # unload tabs when we're low on memory
toolkit.legacyUserProfileCustomizations.stylesheets = true # load userChrome.css
# network.http.sendRefererHeader = 0 # never send referer, this one breaks a lot of signins, don't use it.

userChrome.css

#tabbrowser-tabs {
  visibility: collapse !important; /* Don't show tab bar /*
}