http://stroudceilidhs.co.uk
http://dance.mister.red
http://mister.red/dance23.htm (used in dance.mister.red above in another frame)
FireFox 59.0.2 portable & I think since FF59.0.1 - sticks trying to load one or the other frame. Earlier version (54) is OK. Links in top frame (if visible) load in lower frame when clicked (fortunately) as intended.
Win7 (various broadband connections - mostly BT in the UK)
StroudCeilidhs has not changed for a few weeks. In both instances the underlying format/JavaScript is unchanged, only text would alter (mister.red data change often but the process is automated so unlikely to be different materially) . Scheme unaltered generally for about a year.
The control tests are IE11 and Chrome 40 & 53.0.2785.116 - these exhibit no problems.
Does anyone have any clues to this behaviour
FWIW FireFox 34 doesn't show this anomaly. (debugging issues with later versions!) 
