Its a Ad issue. If you access the site on a iDevice of any type you are presented with an ad that goes to the bottom of the Safari browser and follows you on the scrolling up or down unless you close the ad.
This is something we worked on before and fixed for the phones we tested with. I will take another look at this, but we implemented a media-query that hid the social media toolbar if the screen was a mobile browser width.
Can you let me know what browser the phone uses? And what model phone it is. This may help in getting it resolved.