isNN3 = (navigator.appName == "Netscape" && parseInt(navigator.appVersion)>= 3);
isIE4 = (navigator.appName == "Microsoft Internet Explorer" && parseInt(navigator.appVersion) > 3);


if(isNN3 || isIE4) {
var toursdn = new Image();
toursdn.src = 'images/nav_tours.jpg';
var toursup = new Image();
toursup.src = 'images/nav_tourson.jpg';

var excursiondn = new Image();
excursiondn.src = 'images/nav_excursion.jpg';
var excursionup = new Image();
excursionup.src = 'images/nav_excursionon.jpg';

var agentdn = new Image();
agentdn.src = 'images/nav_agent.jpg';
var agentup = new Image();
agentup.src = 'images/nav_agenton.jpg';

var aboutdn = new Image();
aboutdn.src = 'images/nav_about.jpg';
var aboutup = new Image();
aboutup.src = 'images/nav_abouton.jpg';

var photodn = new Image();
photodn.src = 'images/nav_photos.jpg';
var photoup = new Image();
photoup.src = 'images/nav_photoson.jpg';

var testdn = new Image();
testdn.src = 'images/nav_test.jpg';
var testup = new Image();
testup.src = 'images/nav_teston.jpg';

var resdn = new Image();
resdn.src = 'images/nav_reservations.jpg';
var resup = new Image();
resup.src = 'images/nav_reservationson.jpg';

var contactdn = new Image();
contactdn.src = 'images/nav_contact.jpg';
var contactup = new Image();
contactup.src = 'images/nav_contacton.jpg';

var homedn = new Image();
homedn.src = 'images/nav_home.jpg';
var homeup = new Image();
homeup.src = 'images/nav_homeon.jpg';

}
function act(imgName) {
if(isNN3 || isIE4)
document[imgName].src = eval(imgName + 'up.src')
}

function inact(imgName) {
if(isNN3 || isIE4) 
document[imgName].src = eval(imgName + 'dn.src')
}