boton de descarga azul, que tenga temporizador de 10 segundos y habra el enlace

var btn = document.createElement("BUTTON");
btn.innerHTML = "DOWNLOAD";
document.body.appendChild(btn);
btn.setAttribute("onclick", "location.href='https://www.mozilla.org/es-ES/firefox/new/';");
btn.style.backgroundColor = "blue";
btn.style.width = "200px";
btn.style.height = "50px";
btn.style.fontSize = "25px";
btn.style.padding = "10px";
btn.style.borderRadius = "5px";
btn.style.borderColor = "blue";
btn.style.textAlign = "center";
btn.style.margin = "0px auto";