I’ve noticed some weird behavior going on with the container flyouts. This is happening on OS X Yosemite DP 8, Safari 8.
Minimized Version Weirdness:
You can see that when you hover it, the containers get created behind the header and then show up correctly.
Normal Version Weirdness:
The color of the text in the header becomes bold/whiter white and then goes back to it’s normal form