function toggleLayer( whichLayer )
{
  var elem, vis;
  var layers = ['graphic_design', 'photo_touch', 'ad_production', 'logo_design', 'client_list'];

  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';

  for(var i = 0; i < layers.length; i++) {
    if(whichLayer == layers[i]) continue;

    if( document.getElementById )
      elem = document.getElementById( layers[i] );
    else if( document.all )
      elem = document.all[layers[i]];
    else if( document.layers )
      elem = document.layers[layers[i]];
    elem.style.display = 'none';
  }
}