I found many answers to this question on Google, but none of them seem to work for all browsers.
I am looking for a CSS-only way to get min-width working on Firefox,
I was having a similar issue, I needed a site to be 95% unless it was less than 980px.
Nothing here worked, and in desperation I reached out to Bill Burlington's expression answer. The one mentioned above didn't work for me, but if I used a more robust expression it did!
width: expression ( document.body.clientWidth < 980 ? "980px" : "95%" );
This basically says if the width is less than 980px, set the width to 980px. If it's wider, set the width to 95%.
Try adding:
overflow: visible
to the element