(function($){
    $.fn.verticalMiddle = function(options){
        var op = $.extend({
            visibility: 'visible',
            height    : 9999
        }, options || {});

        $(this).each(function(){
            var h = $(this).height();
            if (h < op.height) {
                var p = (op.height - h)/2;
                $(this).css({'position':'relative','top':p});
            }
            if (op.visibility == 'hidden') {
                $(this).css('visibility','visible');
            }
        });
    };
})(jQuery);