Fixes navbar bug

Hi,

this should fix the following bug.
![bildschirmfoto 2014-03-04 um 18 07 40](https://f.cloud.github.com/assets/5738978/2323675/900bb340-a3bf-11e3-8971-549d66728bb9.png)

@rmetzger: I did not change anything to the pull request I sent to the old repository with the gh-pages branch, because it works for me fine. See picture below. Can you please explain me how to reproduce this bug? I checked every possible width twice.

![bildschirmfoto 2014-03-04 um 18 09 35](https://f.cloud.github.com/assets/5738978/2323691/cd6624fa-a3bf-11e3-8834-c7c717052c8b.png)