just put the "hint" unto a some block, for example <em>. and this
block in your nav ul li or something.
make <li> tag displaying block and position relative
em is a absolute block width:0; left:(li.width);
then jquery:
$('li").hover(function() {
$(this).find("em").animate({width:XX},300);
},function() {
$(this).find("em").animate({width:0},300)
});XX is the width of a hint 300 is a ms for animation effect
