function showhide(id,bt){
    if (document.getElementById){
        obj = document.getElementById(id);
        but = document.getElementById(bt);
        if (obj.style.display == "block"){
            obj.style.display = "none";
            but.value = "Exibir formulário de email"  
        } else {                      
            obj.style.display = "block";
            but.value = "Esconder formulário de email"
        }
    }
}