When one pops up in the top left there is a little cog icon, which brings up a menu.
1. Click disable.
2. then choose for all sites and hit save.
To stop other people having to deal with them on your LJ turn off the option in your Viewing Options
Thanks to
thesaltywench for asking the quesiton in her LJ and for snell_mouse and tro_lo_loki for answering it. 