(function($) {
    $.fn.center = function(settings) {
        var style = $.extend({
            position: 'absolute', //absolute or fixed
            top: '50%',            //50% is center
            left: '50%',
            zIndex: 2009,
            relative: true        
        }, settings || {});

        return this.each(function() {
            var $this = $(this);

            if (style.top == '50%') style.marginTop = -$this.outerHeight() / 2;
            if (style.left == '50%') style.marginLeft = -$this.outerWidth() / 2;
            if (style.relative && !$this.parent().is('body') && $this.parent().css('position') == 'static')
                $this.parent().css('position', 'relative');
            delete style.relative;
            //ie6
            if (style.position == 'fixed' && $.browser.version == '6.0') {
                style.marginTop += $(window).scrollTop();
                style.position = 'absolute';
                $(window).scroll(function() {
                    $this.stop().animate({
                        marginTop: $(window).scrollTop() - $this.outerHeight() / 2
                    });
                });
            }

            $this.css(style);
        });
    };
})(jQuery);