Why is there a line through the social sharing boxes?

I'm currently hosting a website called "Ultradapt" - can be found at www.ultradapt.com. And I am in the process of setting up some social sharing buttons to generate more traffic.

However, I've stumbled onto a problem regarding the social sharing buttons. If you take a look at the website above, there is a white line through the buttons. Why is this line showing, and how do I disable it?

Thank you so much for your help in advance. I'm truly thankful!