Try resizing the page to the URL attached.
As you see, the initial state of the links in the list is "display: inline". When the window is smaller than 740px the display property is changed to block, thus making the list items list vertically. When you size up the window again to above 740px the list is supposed to return to the initial state which is what doesn't happen.
This looks quite similar to another bug:
"Element still flowed below parent after changing from block to inline-block"
*** This bug has been marked as a duplicate of bug 74976 ***