function showhide(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';
}

function show(whichLayer) {
  document.getElementById(whichLayer).style.display='block';
}

function hide(whichLayer) {
  document.getElementById(whichLayer).style.display='none';
}