function toggleLayer(layer, text, text1, text2)
{
  var style = document.getElementById( layer ).style;
  var textB = document.getElementById( text );
  if (textB.nodeName == 'IMG') {
    var attSrc = textB.attributes.getNamedItem("src");
    attSrc.value = (attSrc.value!=text1)?text1:text2;
  } else {
    textB.innerHTML = (textB.innerHTML!=text1)?text1:text2;
  }
  style.display = (style.display!='block')?'block':'none';
}