When reading the Tour of Scala on an iPhone 5, and I zoom in to the content so that the actual text fills the screen, the table of contents starts out in the right position, but when I scroll down, the table of contents jumps far to the right, almost off screen. It then stays offscreen even if I try to scroll to the right to see it. Combined with #390 it is really hard to read the Tour on an iPhone.

Initial position:

After scrolling down