var logo = document.getElementById('logo');
var topbarlogo = document.getElementById('topbarlogo');

function showLogo(){

	if(window.pageYOffset)
		var display = window.pageYOffset - 70;
	else
		var display = document.documentElement.scrollTop - 70;
	
	
	if(0 < display){
		topbarlogo.style.visibility = 'visible';
	}	
	else {
		topbarlogo.style.visibility = 'hidden';
	}
}

setInterval('showLogo()', 200);