"Backend error!" for combined search examples
The combined search examples on https://atlas.torproject.org/#about result in this error for me on both Firefox 36.0.1 and Safari 7.1.3:
The backend server replied with an error to your query. This probably means that you did not properly format your query. If your query was properly formatted it may mean that there is an issue with your browser/add-ons. Please report which browser/addons/etc. you're using to the bug tracker.
Custom combined searches like "flag:Authority country:us" result in the error.