os/browser: mac os / firefox

problem: upon exiting a project overlay, the horizontal scroll layout seems to reset. problem exists on chrome as well.

also, i think the current setup for side margins doesn't play too well with horizontal scroll.. i want a list of 20+ items as a scrollable band, but having side margins means that after the first 4 thumbnails, there's an uneven margin between images.. as a work around, i can enter a value for the left margin and 0 for the right, and then set column gutter to the same value, but this doesn't cover a fix for all cases.