function showLayer(idName){ 
  if(document.getElementById) //NN6,Mozilla,IE5用
    document.getElementById(idName).style.visibility = 'visible'
  else if(document.all)       //IE4用
    document.all(idName).style.visibility = 'visible'
  else if(document.layers)    //NN4用
    document.layers[idName].visibility = 'show'
}
function hiddenLayer(idName){ 
  if(document.getElementById) //NN6,Mozilla,IE5用
    document.getElementById(idName).style.visibility = 'hidden'
  else if(document.all)       //IE4用
    document.all(idName).style.visibility = 'hidden'
  else if(document.layers)    //NN4用
    document.layers[idName].visibility = 'hidden'
}