jQuery.preloadImages = function()
{
 for(var i = 0; i<arguments.length; i++)
 {
  jQuery("<img>").attr("src", arguments[i]);
 }
};
$.preloadImages("images/navi_about_on.jpg","images/navi_expertise_on.jpg","images/navi_news_on.jpg","images/navi_projects_on.jpg","images/navi_contact_on.jpg");

$(document).ready(function() {
$('.navi').hover(function() {
	
	activeSrc = $(this).attr("src");
	activeSrc = activeSrc.replace("_off","_on");
	$(this).attr("src",activeSrc);
		}, function() {
	activeSrc = $(this).attr("src");
	activeSrc = activeSrc.replace("_on","_off");
	$(this).attr("src",activeSrc);
});
});