As you can see in the attached screenshot, the horizontal line beneath the workboard header seems to tear at the workboard column boundaries.
This is on firefox 39.0. It looks fine in chrome.
My install is at head as of a few minutes ago:
Phabricator Version bb54957d9687a9278caae41b2f0918de548254a6 Arcanist Version 999eb93765688a788b77513334cc9a651726c94b libphutil Version aa6cd8f7e5e5e637dcfcb8417fbc343b45820c93
I do not see this issue on secure.phab, but I know you guys aren't always running head here.