var tmp = (navigator.appName == "Microsoft Internet Explorer") ? document.getElementsByTagName("object") : document.getElementsByTagName("embed");
var elem = tmp[0];

elem.style.position = "absolute";
elem.style.left = "50%";
elem.style.top = "50%";

var tmpX = "-" + (elem.width / 2) + "px";
var tmpY = "-" + (elem.height / 2) + "px";

elem.style.marginLeft = tmpX;
elem.style.marginTop = tmpY;