img1 = new Image(121,18);
img1.src = url_address + "images/buttons/contact-off.gif";
img2 = new Image(121,18);
img2.src = url_address + "images/buttons/contact-on.gif";

img3 = new Image(68,18);
img3.src = url_address + "images/buttons/join-off.gif";
img4 = new Image(68,18);
img4.src = url_address + "images/buttons/join-on.gif"; 

function changeimage(imgx,placex) {
  if (document.images) {
    document.images[placex].src = eval(imgx + ".src");
  }
}