var preloadFlag = false;
function preloadImages() {
	if (document.images) {
		pre_nav_contact_on = newImage('images/nav_contact_on.jpg');
		pre_nav_projects_on = newImage('images/nav_projects_on.jpg');
		pre_nav_about_on = newImage('images/nav_about_on.jpg');
		pre_nav_drainage_on = newImage('images/nav_drainage_on.jpg');
		pre_nav_excavation_on = newImage('images/nav_excavation_on.jpg');
		pre_nav_clearing_on = newImage('images/nav_clearing_on.jpg');
		pre_nav_concrete_on = newImage('images/nav_concrete_on.jpg');
		pre_nav_milling_on = newImage('images/nav_milling_on.jpg');
		pre_nav_paving_on = newImage('images/nav_paving_on.jpg');
		preloadFlag = true;
	}
}