algo asi ocupan?
Código HTML:
Ver original<script type="text/javascript"> function ocultar(){
document.getElementById("1").style.visibility="hidden";
document.getElementById("2").style.visibility="hidden";
document.getElementById("3").style.visibility="hidden";
}
function fon(a){
if(a != ""){
document.getElementById(a).style.visibility="";
}
}
<body onload="ocultar()">
<select id="telefono" onchange="ocultar();fon(document.getElementById('telefono').value)"> <input type="button" value="agregar" onclick="fon(document.getElementById('telefono').value)"/> <div id="2" style.display="none"> <div id="3" style.display="none">