Display of 2nd menu and breadcrumb trail
I looked for an existing thread about this, in the belief that I cannot be the only person to have the following problem, but I found nothing.
The search region encroaches upon the secondary menu, which makes some of its links (Forum actions onwards) unreachable, and the last link in the secondary menu drops down and causes exactly the same problem for the breadcrumb trail. I have the base font size increased (that is something else that you ought to review, actually) but I have ensured that this is not the cause. I use Firefox, but Chrome is just the same.
Basically, the entire menu and search region layout seems to be designed for very wide viewports and fails to shrink gracefully.