CSS fix for small screen sizes, e.g. on mobile phones

see #319

This is needed for e.g. mobile phones

before:

![sync01](https://cloud.githubusercontent.com/assets/71315/3145027/fdbe8a6e-ea2f-11e3-96f1-0d4518eb817c.JPG)

after:

![sync02](https://cloud.githubusercontent.com/assets/71315/3145028/0374e160-ea30-11e3-9e68-7ab2ef7c11a4.JPG)