if (navigator.appVersion.indexOf("2.") != -1){
        check = false;
        }
if ((navigator.appVersion.indexOf("3.") != -1) && (navigator.appName.indexOf("Explorer") != -1)){
        check = false;
        }
else {
        check = true;
        }

var NN3 = false;
image1= new Image();
image1.src = "/resources/graphics/button-main-off.gif";
image1on = new Image();
image1on.src = "/resources/graphics/button-main-on.gif";
image2= new Image();
image2.src = "/resources/graphics/button-about-off.gif";
image2on = new Image();
image2on.src = "/resources/graphics/button-about-on.gif";
image3= new Image();
image3.src = "/resources/graphics/button-textbook-off.gif";
image3on = new Image();
image3on.src = "/resources/graphics/button-textbook-on.gif";
image4= new Image();
image4.src = "/resources/graphics/button-resources-off.gif";
image4on = new Image();
image4on.src = "/resources/graphics/button-resources-on.gif";
image5= new Image();
image5.src = "/resources/graphics/button-testcenter-off.gif";
image5on = new Image();
image5on.src = "/resources/graphics/button-testcenter-on.gif";

function imageon(name)   {
        document[name].src = eval(name + "on.src");
}
function imageoff(name)  {
        document[name].src = eval(name + ".src");
}
NN3 = true;

function on(name)  {
        if (check == true){
                imageon(name);}
}
function off(name)  {
        if (check == true){
                imageoff(name);}
}