jQuery.fn.center = function (absolute) {
    return this.each(function () {
        var t = jQuery(this);
        t.css({
            position:absolute ? 'absolute' : 'fixed', 
            left:'50%', 
            top:'50%', 
            zIndex:'999999'
        }).css({
            marginLeft:'-' + (t.outerWidth() / 2) + 'px', 
            marginTop:'-' + (t.outerHeight() / 2) + 'px'
        });

        if (absolute) {
            t.css({
                marginTop:parseInt(t.css('marginTop'), 10) + jQuery(window).scrollTop(), 
                marginLeft:parseInt(t.css('marginLeft'), 10) + jQuery(window).scrollLeft()
            });
        }
    });
};