Layout with Arctic template broken on Firefox

[ghost]

I'm using the Arctic theme along with pagequery, and the layout happens to be broken on Firefox (and other Gecko-based browsers). Specifically, pagequery elements always seem to be pushed towards the right and reduced in size.

I initially had reported this at Mozilla, but since the bug has been marked as a duplicate of another bug which has not been fixed for three years(!), I would like you to come up with some kind of a fix.