404. That’s an error.

The requested URL /bookmarks/mark?op=add&title=Station+P543+%28CentralCalifornia+Network%29&annotation=&nui=1&service=bookmarks&bkmk=http%3A%2F%2Fearthquake.usgs.gov%2Fmonitoring%2Fgps%2FCentralCalifornia%2Fp543%2F was not found on this server. That’s all we know.