A list featuring display-on-hover, media queries and a fixed grand-parent renders nicely in certain max-width conditions, but fails to clean up rendered boxes in another.
STEPS TO REPRODUCE
1) View example page at http://mlab.taik.fi/~jon/glitch/ using a viewport width larger than 990px.
2) Hover over top menu items to observe correct behaviour
3) Decrease viewport width to less than 990px to activate a collapsed version of the top menu.
4) Hovering over menu icons renders submenus, but fails to completely clear them on exit.
(Works as expected in Firefox and Opera.)
The example page is unfortunately not a complete test case reduction.
Created attachment 44298 [details]
Example page for bug 29805
Here's a reduction. In this example page, when viewed using a viewport > 500px, the dropdown menus appear while hovering the menu items and clear on mouse exit. After resizing the viewport to < 500px, the menus appear as expected, but fail to clear.