if (document.images) {

        nav1on = new Image();
        nav1on.src = "images/nav-home-on.gif"; 
        nav1off = new Image();
        nav1off.src = "images/nav-home-off.gif";
        nav2on = new Image();
        nav2on.src = "images/nav-bio-on.gif"; 
        nav2off = new Image();
        nav2off.src = "images/nav-bio-off.gif";
        nav3on = new Image();
        nav3on.src = "images/nav-contact-on.gif"; 
        nav3off = new Image();
        nav3off.src = "images/nav-contact-off.gif";

}
function changeImages(){
        if(document.images){
                for (var i=0; i<changeImages.arguments.length; i+=2) {
                        document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
                }
        }
}