function hidelayers() {

elm1 = document.getElementById("Layer1");
elm1.style.visibility="hidden";

elm2 = document.getElementById("Layer2");
elm2.style.visibility="hidden";

elm3 = document.getElementById("Layer3");
elm3.style.visibility="hidden";

elm4 = document.getElementById("Layer4");
elm4.style.visibility="hidden";

elm5 = document.getElementById("Layer5");
elm5.style.visibility="hidden";
}

function showlayer(num) {
hidelayers();
elm1 = document.getElementById(num);
elm1.style.visibility="visible";
}