var SiteWidth = 998;
var sLeft = (document.body.clientWidth - SiteWidth) / 2;
if (sLeft < 0 ){sLeft = 0;}
 
function NewLeft(sName){
	var elem = document.getElementById(sName);
	if (elem){var nLeft = elem.offsetLeft + sLeft; elem.style.left = nLeft + 'px';}
}

 //site
 NewLeft('abonnement');