(function($) {

$.fn.flipNav = function(options) {

options = $.extend({
speed : 200
}, options);

return this.each(function() {

var nav = $(this),
lis = $('li', nav),
anchors = $('a', lis).css('padding', 0),
spanHeight;

$.each(anchors, function() {
var a = $(this),
val = a.text();

a.html('<span>' + val + '</span> <span>' + val + '</span>')
.parent('li')
.height(a.children('span:first').outerHeight())
.end()
.children('span:first')
.css('marginTop', 0) // strange for IE
});

spanHeight = lis.eq(0).height();

lis.hover(function() {
$(this).find('span:first').animate({
marginTop : '-' + spanHeight
}, { duration: options.speed, queue : false });
}, function() {
$(this).find('span:first').animate({
marginTop : 0
}, { duration: options.speed, queue: false });
});

}); // end each

}

})(jQuery);