I use a Chromebook and can't install Firefox on it, so I use an old computer with Firefox v 48.0.2 to compare to other browsers. I have also tested with a fresh install of the latest version of Firefox and got the same results.
I have a Huge-IT slider plug-in installed on a Wordpress site that I add content to. I don't have complete access as an administrator but can make changes to the sliders installed in the plug-in. I find that with Firefox, the size of the slider is displayed larger than other browsers. If it is too large, it will not display at all, though other browsers will shrink it as needed to fit it in it's correct position on the page. A solution that allows it to display in Firefox is to reduce the width/height to fit with little extra horizontal space. But in other browsers, the slider appears smaller than the space allowed. This is on the Home page that uses wigits to display content.
Previously, I had loaded the slider with slides with an incorrect aspect ratio. While other browsers displayed the slides with distortions, Firefox did not display the slider at all. I also have a slider on another page that has content loaded directly on the page using the slider's shortcode, and there I had no problem with Firefox.
Thanks, Dane