You can set the system-wide default browser in GNOME 3 under Activities ▸ Applications ▸ System Settings ▸ System ▸ System Info ▸ Default Applications.
If the preferred browser is set as default application but still does not work correctly please contact your distribution via their forum or bug tracker.
GNOME 3 users with a technical background can tweak these settings by defining scheme-handlers in $HOME/.local/share/applications/mimeapps.list.
If the error message "Could not open the link: Operation not supported" is shown, you need to install the package gvfs.
