var nav= new Array("images/home_down.jpg","images/portfolio_down.jpg","images/services_down.jpg","images/about_down.jpg","images/contact_down.jpg","images/blog_down.jpg");

var preload = new Array();

for (var i=0; i<nav.length; i++)
{
preload[i]= new Image();
preload[i].src=nav[i];
}