if (document.images) {

nav_summer_on = new Image();
nav_summer_on.src = "../images/nav_summer_on.jpg";
nav_summer_off = new Image();
nav_summer_off.src = "../images/nav_summer_off.jpg";

nav_teacher_on = new Image();
nav_teacher_on.src = "../images/nav_teacher_on.jpg";
nav_teacher_off = new Image();
nav_teacher_off.src = "../images/nav_teacher_off.jpg";

nav_concert_on = new Image();
nav_concert_on.src = "../images/nav_concert_on.jpg";
nav_concert_off = new Image();
nav_concert_off.src = "../images/nav_concert_off.jpg";

nav_about_on = new Image();
nav_about_on.src = "../images/nav_about_on.jpg";
nav_about_off = new Image();
nav_about_off.src = "../images/nav_about_off.jpg";

nav_support_on = new Image();
nav_support_on.src = "../images/nav_support_on.jpg";
nav_support_off = new Image();
nav_support_off.src = "../images/nav_support_off.jpg";

nav_contact_on = new Image();
nav_contact_on.src = "../images/nav_contact_on.jpg";
nav_contact_off = new Image();
nav_contact_off.src = "../images/nav_contact_off.jpg";

sub_summer_on = new Image();
sub_summer_on.src = "../images/sub_summer_on.jpg";
sub_summer_off = new Image();
sub_summer_off.src = "../images/sub_summer_off.jpg";

sub_teacher_on = new Image();
sub_teacher_on.src = "../images/sub_teacher_on.jpg";
sub_teacher_off = new Image();
sub_teacher_off.src = "../images/sub_teacher_off.jpg";

sub_spotlight_on = new Image();
sub_spotlight_on.src = "../images/sub_spotlight_on.jpg";
sub_spotlight_off = new Image();
sub_spotlight_off.src = "../images/sub_spotlight_off.jpg";



}
function turnOn(imgName) {
        if (document.images) {
        	document[imgName].src = eval(imgName + "_on.src");
        }
}
function turnOff(imgName) {
        if (document.images) {
        	document[imgName].src = eval(imgName + "_off.src");
        }
}