The problem comes from a number of CSS styles that contain this code:

display:table-cell;

I was able to simply remove this line of CSS whereever it occurred, and the problem seems to be resolved.

Anyone know why it was included in the first place?  Surely there was a good reason.

There is another thread in this forum regarding this problem which explains exactly how to solve this simply by altering a couple of lines of css for each icon. You can then choose whether you want to align the icons horizontally left or right. However, the icons will not display horizontally center. Can't recall the css but do a search for Firefox within this forum and I'm sure you'll find it.

Luckily for me, align right is perfect for my design.

Jess