function vedicerca(whichLayer) {
  var elem, vis;
  if(document.getElementById)
    elem = document.getElementById(whichLayer);
  else if(document.all)
      elem = document.all[whichLayer];
  else if(document.layers)
      elem = document.layers[whichLayer];
  vis = elem.style;
  if(vis.display==''&&elem.offsetWidth!=undefined&&elem.offsetHeight!=undefined)
    vis.display = (elem.offsetWidth!=0&&elem.offsetHeight!=0)?'block':'none';
  vis.display = (vis.display==''||vis.display=='block')?'none':'block';
}