function toggleLayer(element){
  if (document.getElementById){
    // DOM
    var oStyle = document.getElementById(element).style;
  }
  else if (document.all){
    // msie
    var oStyle = document.all[element].style;
  }
  else if (document.layers){
    // nn4
    var oStyle = document.layers[element].style;
  }
  oStyle.display = oStyle.display? "":"block";
}