function addListener(elemento,baseName,handler) {
    if (elemento.addEventListener)
        elemento.addEventListener(baseName,handler,false);
    else if (elemento.attachEvent)
        elemento.attachEvent('on'+baseName, handler)
}
function remListener(elemento,baseName,handler) {
    if (elemento.removeEventListener)
        elemento.removeEventListener(baseName,handler,false);
    else if (elemento.attachEvent)
        elemento.detachEvent('on'+baseName, handler)
}
     
function referrer() {
    if (document.getElementById("torna"))
        document.getElementById("torna").setAttribute("href",document.referrer);
}

               
addListener(window, 'load', referrer);