[ruslan_mart]

Что значит обернуть в onload/DOMContentLoaded ???

window.addEventListener('DOMContentLoaded', function() {
	var elem = document.querySelector('.name'),
		body = document.body,
		html = document.documentElement;

	this.addEventListener('scroll', function() {
		var scrollHeight = (html.scrollHeight || body.scrollHeight) - this.innerHeight,
			scrollTop = html.scrollTop || body.scrollTop || 0;
		elem.style.opacity = 1 - 1 / scrollHeight * scrollTop;
	});
});