function centerDiv(div) {
    if (div) {
        var scrolledX, scrolledY;
        if (self.pageYoffset) {
            scrolledX = self.pageXoffset;
            scrolledY = self.pageYoffset;
        } else if (document.documentElement && document.documentElement.scrollTop) {
            scrolledX = document.documentElement.scrollLeft;
            scrolledY = document.documentElement.scrollTop;
        } else if (document.body) {
            scrolledX = document.body.scrollLeft;
            scrolledY = document.body.scrollTop;
        }
        var centerX, centerY;
        if (self.innerHeight) {
            centerX = self.innerWidth;
            centerY = self.innerHeight;
        } else if (document.documentElement && document.documentElement.clientHeight) {
            centerX = document.documentElement.clientWidth;
            centerY = document.documentElement.clientHeight;
        } else if (document.body) {
            centerX = document.body.clientWidth;
            centerY = document.body.clientHeight;
        }
        var w = (div.offsetWidth) ? div.offsetWidth : div.clientWidth;
        var h = (div.offsetHeight) ? div.offsetHeight : div.clientHeight;
        var leftoffset = scrolledX + (centerX - w) / 2;
        var topoffset = scrolledY + (centerY - h) / 2;
        div.style.position = 'absolute';
        div.style.top = topoffset + 'px';
        div.style.left = leftoffset + 'px';
    }
}