Black Scrolling Button

Hi,
im really happy with your thubmnail scroller, but when implementing it the Buttons are just Black Boxes (see Screenshot) no matter what HTML I user for them.
<img width="138" alt="screen shot 2017-02-07 at 12 02 55" src="https://cloud.githubusercontent.com/assets/5067446/22688627/6476a676-ed2d-11e6-91fe-c96a8664745b.png">
