function showLayer(layerName, shadowLayerName, tabLayer)
  {
    if (document.getElementById)
      {
        var targetElement = document.getElementById(layerName);
        var shadowElement = document.getElementById(shadowLayerName);
        var tabElement = document.getElementById(tabLayer+'Tab');
        targetElement.style.top = shadowElement.style.top;
        targetElement.style.display = 'inline';
        var oldSRC = tabElement.src;
        var newSRC = oldSRC.replace(tabLayer+'Up', tabLayer+'Down');
        tabElement.src = newSRC;
      }
  }

function hideLayer(layerName, tabLayer)
  {
    if (document.getElementById && document.getElementById(layerName)) 
      {
        var targetElement = document.getElementById(layerName);
        var tabElement = document.getElementById(tabLayer+'Tab');				
        targetElement.style.display = 'none';
        var oldSRC = tabElement.src;
        var newSRC = oldSRC.replace(tabLayer+'Down', tabLayer+'Up');
        tabElement.src = newSRC;
      }
  }