function toggleLayer( whichLayer )

{

  var elem, vis;

  if( document.getElementById ) // this is the way the standards work

    elem = document.getElementById( whichLayer );

  else if( document.all ) // this is the way old msie versions work

      elem = document.all[whichLayer];

  else if( document.layers ) // this is the way nn4 works

    elem = document.layers[whichLayer];

  vis = elem.style;

  // if the style.display value is blank we try to figure it out here

  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';

}