Overlap
Visiting Special:MobileOptions on a Firefox OS device you'll notice that the labels overlap the checkboxes.
The issue seems to be because the width does not apply to the invisible (opacity:0) input[type=checkbox] and as a result it doesn't make enough room for the pseudo element.
Confirmed in the Firefox OS developer preview phone we have in the office.
See also: https://bugzilla.mozilla.org/show_bug.cgi?id=1078393
Version: unspecified
Severity: normal
Attached: