var winW;
var max=1000;
var left;


if (parseInt(navigator.appVersion)>3) {
 if (navigator.appName.indexOf("Microsoft Internet Explorer")!=-1) {
  winW = document.body.offsetWidth;
 }
else {
  winW = window.innerWidth;
   }
}

var marg=(winW-max)/2;

if (winW >= max){ display = max+"px"}
else {display = "auto";}

if (winW >= max){left=marg+"px"}
else{left = "auto";}

var width = ('<div style="width:' + display + ';margin:0 0 0 '+ left + '">');

document.write(width)