if (document.images) {
   top_of_page_on     = new Image();
   top_of_page_on.src = "top2.gif";
   top_of_page_off    = new Image();
   top_of_page_off.src = "top1.gif";
}

function tnImgOn(imgName) {

}

function tnImgOff(imgName) {

}

function tnCopyOn(imgName) {

}

function tnCopyOff(imgName) {

}