link01=new Image();
   link01.src="pictures/mapa_background_red.png";
   link02=new Image();
   link02.src="pictures/am.png";
   link03=new Image();
   link03.src="pictures/af.png";
   link04=new Image();
   link04.src="pictures/eu.png";
   link05=new Image();
   link05.src="pictures/au.png";
   link06=new Image();
   link06.src="pictures/as.png";

function World()   {document.images[0].src='pictures/mapa_background_red.png'; return true;}
function america() {document.images[0].src='pictures/am.png'; return true;}
function africa() {document.images[0].src='pictures/af.png'; return true;}
function europe() {document.images[0].src='pictures/eu.png'; return true;}
function australia() {document.images[0].src='pictures/au.png'; return true;}
function asia() {document.images[0].src='pictures/as.png'; return true;}