jQuery.fn.centerToWindow = function() {
    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 leftoffset = scrolledX + (centerX - this.width()) / 2;
    var topoffset = scrolledY + (centerY - this.height()) / 2;
    this.css({
        'position': 'absolute',
        'top': topoffset + 'px',
        'left': leftoffset + 'px'
    });
    return this;
}