In Safari, it looks like rounding differences are producing a pixel wide border on either side of #inner-wrap, depending on the browser width. When then background is dark, like your demos, it is hardly noticable (except it does overlap the .is-active arrow - see attached). If you wratchet up the contrast however, the gaps become clear.
Great work here - I like what you've got so far.
In Safari, it looks like rounding differences are producing a pixel wide border on either side of #inner-wrap, depending on the browser width. When then background is dark, like your demos, it is hardly noticable (except it does overlap the .is-active arrow - see attached). If you wratchet up the contrast however, the gaps become clear.
Nothing I've tried was successful. Any thoughts?