[CentOS] Buttons too big in Firefox for Linux

Wed Feb 1 14:32:53 UTC 2017
Gary Stainburn <gary at ringways.co.uk>

A while back, after doing a yum update, a new version of Firefox was installed 
and since then, the contents of my pages don't fit any more because the 
buttons are now much bigger.

I've done some searching and to be honest I've drowned in the results.  To 
make matters worse, most of the results are OLD, referring to IE version 6 
and Firefox version 30.

This problem is only very recent (months).  The problem is only in Firefox for 
Linux. Firefox for Android and Windows look fine, as does Chrome on 
everything and I.E.

Does anyone have any relevant / current suggestions on how to fix this?  
Firefox on Linux is my main development platform so having it look different 
to everything else is a real pain

It doesn't seem to matter whether I use <input type=button> or <button 
type=button>