a_off = new Image(69, 20);
a_off.src = "images/bt_about.gif";
a_on = new Image(69, 20);
a_on.src = "images/bt_about_on.gif";

b_off = new Image(129, 20);
b_off.src = "images/bt_web.gif";
b_on = new Image(129, 20);
b_on.src = "images/bt_web_on.gif";

c_off = new Image(95, 20);
c_off.src = "images/bt_art.gif";
c_on = new Image(95, 20);
c_on.src = "images/bt_art_on.gif";

d_off = new Image(69, 20);
d_off.src = "images/bt_packages.gif";
d_on = new Image(69, 20);
d_on.src = "images/bt_packages_on.gif";

e_off = new Image(64, 20);
e_off.src = "images/bt_contact.gif";
e_on = new Image(64, 20);
e_on.src = "images/bt_contact_on.gif";


function imageReplace(imgid, imgnew) {
    document.images[imgid].src = eval(imgnew + ".src");
}