function layerVisivel(nome) {
    if (document.layers) {
        if (document[nome].display == "block")
            return true;
    } else if (document.all) {
        if (document.all[nome].style.display == "block")
            return true;
    } else if (document.getElementById) {
        if (document.getElementById(nome).style.display == "block") 
            return true;        
    }
    return false;
}  

function mostraLayer(nome) {
   if (document.layers)
       document[nome].display = "block";
   else if (document.all)
       document.all[nome].style.display = "block";
   else if (document.getElementById)
       document.getElementById(nome).style.display = "block";
}

function ocultaLayer(nome) {
    if (document.layers)
        document[nome].display = "none";
    else if (document.all)
        document.all[nome].style.display = "none";
    else if (document.getElementById)
        document.getElementById(nome).style.display = "none";
}

function mostraConteudo() {
  mostraLayer("conteudo");
}