function Fensterweite() 
{
	var breite = 0;
	if (window.innerWidth) 
	{
		breite = window.innerWidth;
	} 
	else 
		if (document.body && document.body.offsetWidth) 
		{
			breite = document.body.offsetWidth;
		} 
	if(breite < 821)
		breite = 821;
	return breite;
}

function posLogo()
{
	document.getElementById("logo_ani").style.left = (Fensterweite() / 2 - 150) + "px";
	document.getElementById("logo_ani").style.visibility = "visible";
}

if (!window.Weite && window.innerWidth) 
{
	window.onresize = posLogo;
}