[CentOS] Buttons too big in Firefox for Linux

On Thursday 02 February 2017 06:21:41 geo.inbox.ignored wrote:
> On 02/01/2017 08:32 AM, Gary Stainburn wrote:
> > 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.
>
> }}
>
> which buttons? frame or web page?

It appears to be any <input type=button> or <button> anywhere on the page, 
whether inside DIV's, Frames or not.

They're only slightly bigger than they should be but it's enough to break page 
layouts.

I've been doing some more reading and it appears that it's something to do 
with the default CSS for the web browser, as I don't have a "reset" section 
at the top of my CSS. Maybe that's my fault, but the bigger picutre question 
is "why does Firefox for Linux" show different to everyone else, including 
Firefox on any other platform?