function navigation_on(button_name,site_url) {
   document.getElementById('img_' + button_name).src=site_url+'/images/home/links/' + button_name + '_hover.jpg';
	}
function navigation_off(button_name,site_url) {
   document.getElementById('img_' + button_name).src=site_url+'/images/home/links/' + button_name + '.jpg';
	}