function preload(imgObj,imgSrc) {
	if (document.images) {
		eval(imgObj+' = new Image()')
		eval(imgObj+'.src = "'+imgSrc+'"')
	}
}

preload('introUp','../../graphic/nav/introduction.gif')
preload('introDn','../../graphic/nav/introduction-on.gif')
preload('aboutUp','../../graphic/nav/about.gif')
preload('aboutDn','../../graphic/nav/about-on.gif')
preload('productUp','../../graphic/nav/catalogue.gif')
preload('productDn','../../graphic/nav/catalogue-on.gif')
preload('materialUp','../../graphic/nav/materials.gif')
preload('materialDn','../../graphic/nav/materials-on.gif')
preload('orderUp','../../graphic/nav/ordering.gif')
preload('orderDn','../../graphic/nav/ordering-on.gif')
preload('contactUp','../../graphic/nav/contact.gif')
preload('contactDn','../../graphic/nav/contact-on.gif')

function changeImage(layer,imgName,imgObj) {
	if (document.layers && layer!=null) eval('document.'+layer+'.document.images["'+imgName+'"].src = '+imgObj+'.src');
	else document.images[imgName].src = eval(imgObj+".src");
}