Social box disappearing

socialBox.js

window.onscroll = function(){scrollStop()};

function scrollStop(){
	var socialBox = document.getElementsByClassName("indexadv")[0];
	var breakingPoint = document.body.offsetHeight - document.getElementById("footer").offsetHeight;
	var socialBoxHeight = socialBox.clientHeight;
	if ((document.body.scrollTop + socialBoxHeight + 50) > breakingPoint){
		socialBox.style.display = "none";
	} else {
		socialBox.style.display = "block";
	}
}