<!------------------ esconde/exibi divs ---------------------->
     function show_div(div) {
if (document.getElementById(div).style.visibility == "hidden") {
   document.getElementById(div).style.visibility = "visible";
   document.getElementById(div).style.position = "relative";
}
else {
   document.getElementById(div).style.visibility = "hidden";
   document.getElementById(div).style.position = "absolute";
}     }