$(document).ready(function(){
   $('.navButton').hover(
   function() {
   	orig = $(this).find("img").attr("src");
   	if(orig.substr(orig.length - 9, 9) != '_down.gif') {
   		$(this).find("img").attr("src", orig.substr(0, orig.length - 4) + '_down.gif');
   	}
   },
   function() {
   	orig = $(this).find("img").attr("src");
   	if(orig.substr(orig.length - 9, 9) == '_down.gif' && !($(this).hasClass('navButtonSelected'))) {
   		$(this).find("img").attr("src", orig.substr(0, orig.length - 9) + '.gif');
   	}
   });
 });